agro-terrorism. Terrorism by contaminating crops or livestock with a deadly contagious disease.

American Airlines Flight 11. Crashed Sept. 11 into north tower of World Trade Center. Hijacked en route from Boston to Los Angeles. Suspected hijackers were Wail M. Alshehri, Waleed M. Alshehri, Mohamed Atta, Satam al-Suqami and Abdulaziz Alomari.

American Airlines Flight 77. Crashed Sept. 11 into the Pentagon. Hijacked en route from Washington-Dulles International Airport to Los Angeles. Suspected hijackers were Khalid al-Midhar, Majed Moqed, Nawaq Alhazmi, Salem Alhazmi and Hani Hanjour.

anthrax. Deadly bacterium used in apparent bioterrorist attacks since Sept. 11. Anthrax can infect by inhalation or skin contact (cutaneous infection). It is treatable with antibiotics, primarily doxycycline and Cipro. If diagnosed early, the patient has a strong probability of full recovery.

anti-terrorism. Anti-terrorism efforts are preventive measures, such as judicial, legislative, security or military measures taken to reduce vulnerability to a terrorist attack, as contrasted with counter-terrorism measures, which are military, police and intelligence measures used to fight terrorism through pre-emptive or retaliatory measures.

assassination. Terrorist groups may engage in assassination, but assassination is not terrorism. Assassination has a specific target, though other people may be killed or injured. Terrorists target a group of people, but generally choose specific victims randomly. If the Sept. 11 attack had succeeded in killing President Bush, it would have involved assassination and terrorism. President Ford banned CIA involvement in assassinations with a 1976 executive order, after a congressional investigation revealed evidence of a plot to kill Fidel Castro. Some U.S. leaders want to repeal the order.

Atlanta. Site of still-unsolved bombing at Centennial Olympic park during 1996 Summer Olympics. Security guard Richard Jewell was identified publicly as a suspect, but later was cleared. No terrorist group took credit. One person was killed and 111 were injured. In 1998, a federal complaint charged Eric Robert Rudolph with the crime.

Atta. Mohamed Atta is suspected of being the ringleader of the 19 terrorists who died in the Sept. 11 hijackings.

Aum Shinrikyo. Japanese cult that released sarin nerve gas in subway in 1995, killing 12.

bin Laden. Osama (also spelled Usama) bin Laden, a Saudi native, was the 17th of 24 sons of Saudi Arabia's leading builder, Yemeni immigrant Mohammed bin Oud bin Laden. Osama's share of the family wealth has been estimated at $300 million, though some say that figure is too high. He helped the mujahedeen in their war with the Soviet Union, mostly by building facilities and helping recruit other Arabs. His hatred of the United States stems from his view that U.S. forces desecrated holy ground in Saudi Arabia with their presence in the war against Iraq. He was expelled from Saudi Arabia in 1991, then from Sudan in 1996. Since 1996 he has operated terrorist training camps in Afghanistan. His worldwide network, al Qaeda, is blamed for the Sept. 11 attack on the United States, the 2000 attack on the USS Cole and other terrorist attacks. Osama means "like a lion."

bioterrorism. Terrorism using deadly bacteria or virus.

Black September. The Palestinian terrorist group that captured and killed members of the Israeli Olympic team at the 1972 Olympics in Munich, West Germany.

botulinum. Bacterium that could be used by terrorists to contaminate food.

cell. Small group working together clandestinely. Contact with other cells of the same organization and even with command structure of the organization is limited.

chlorine dioxide. Chemical used to purify water, which can kill hard-to-destroy bacteria. Used as a gas to clear Hart Senate office building of anthrax contamination.

counter-terrorism. Counter-terrorism measures are military, police and intelligence measures used to fight terrorism through pre-emptive or retaliatory measures, as contrasted with anti-terrorism measures, which are preventive measures to reduce vulnerability to terrorist attacks.

cyanide. Poison feared as a possible agent in chemical terrorism.

Dar es Salaam. Capital of Tanzania and site of U.S. Embassy bombed Aug. 7, 1998, by suicide bombers linked to bin Laden. U.S. Embassy in Nairobi, Kenya, was bombed at the same time. The two embassy attacks killed 301 and injured 5,000. United States retaliated with missile strikes on an abandoned training camp in Afghanistan and a pharmaceutical plant in Sudan, mistakenly thought to be a chemical weapons factory.

Dark Winter. Bioterrorism "war game" exercise that government agencies tried in June. Hypothetical smallpox epidemic spread to 25 states.

drain the swamp. Cliché meaning that you have to clean up the environment in which a terrorist network operates, rather than retaliate in a limited way.

Egyptian Islamic Jihad. Terror group blamed for the 1981 assassination of Egyptian President Anwar Sadat. President Bush identified Egyptian Islamic Jihad in his address to Congress as one of the groups working with al Qaeda.

Entebbe. Perhaps the most celebrated response to terrorism was the surprise raid by Israeli troops at Uganda's Entebbe Airport in 1976. Gunmen demanding the release of Palestinian prisoners hijacked an Air France flight from Athens to Paris. During a week on the ground, the hijackers released 143 passengers but held 103 hostages, mostly Israelis. In a nighttime raid, three C-130 transport planes landed at Entebbe, loaded with Israeli commandos who killed the seven hijackers and 20 Ugandan soldiers, who were suspected of aiding the hijackers. Three hostages and the Israeli commander also died.

al-Fadl. Jamal al-Fadl, who fled to the West after he was caught embezzling from bin Laden's operation, has helped authorities understand how the operation works.

Foreign Intelligence Surveillance Act. 1978 law allows FBI to monitor suspected terrorists or spies without showing probable cause of a crime.

Foreign Terrorist Asset Tracking Center. Abbreviated FTAT. Agency that will track and attempt to seize or freeze terrorist assets around the world.

Gamaa Islamiya (the Islamic Group). Egypt's largest terrorist group. Claimed responsibility for June 1995 assassination attempt on Egyptian President Hosni Mubarak. Signed bin Laden's 1998 fatwa, declaring jihad against the United States.

Hamas. Palestinian terror group seeking to oust Israel from Palestine. Claimed June 1 attack on Tel Aviv night club and Aug. 9 attack on Jerusalem restaurant. The two suicide attacks killed a combined 39 people.

Harakat ul-Mujahedin. On State Department's list of global terrorist groups.

Hizbullah or Hizballah or Hezbollah. Lebanon-based group that bombed U.S. Embassy and Marine barracks in Beirut in 1983.

hate crimes. A crime whose victim is selected because he or she belongs to a group the attacker hates. Some, but not all, hate crimes are acts of terrorism.

hawala. Paperless financial system that al Qaeda is suspected of using. From the Hindi for "in trust," the system works on cash and promises of repayment, making tracing of transactions difficult.

Hydra. Bin Laden's terrorist network frequently is likened to the Hydra, a multi-headed creature of Greek mythology that grew two new heads each time a head was cut off.

Irradiation. Process used to reduce or eliminate disease-causing germs, most often in food. The US Postal Service plans to irradiate mail to combat anthrax.

Islamic Movement of Uzbekistan. One of two groups President Bush identified in his address to Congress as affiliates of al Qaeda.

Islamic Observation Centre. London-based extremist group.

kamikaze. Japanese pilots who flew suicide missions, crashing their planes into American ships were called kamikaze pilots. The term has come to mean any suicide mission, such as the terrorist attacks on U.S. buildings.

al-Khobar Towers. U.S. military apartment complex in Saudi Arabia, attacked in 1996 by suicide bombers linked to bin Laden. Bomb killed 19 and injured 370.

Kurdistan Workers Party. On State Department's list of global terrorist groups.

Lockerbie. Site where Pan Am Flight 103 crashed in Scotland in 1988 after a terrorist sent plastic explosives aboard in a radio in a checked bag.

make a statement. Cliché for the intended meaning of a terrorist attack or the response to a terrorist attack. Same as "send a message."

McVeigh. Timothy McVeigh was executed June 11 for the Oklahoma City bombing.

al-Midhar. Khalid al-Midhar, a suspected terrorist who died on Flight 77. The CIA filmed him in 2000 at a Kuala Lumpur meeting of suspected terrorists that included a man suspected in the bombing of the USS Cole.

millennium plot. Foiled terrorist plot, linked to bin Laden, to bomb Los Angeles International Airport in December 1999.

Munich. Site of 1972 terrorist attack that gained worldwide attention during the Summer Olympics in Munich, West Germany. Eleven Israeli athletes and coaches were killed in the incident, which began with their abduction in the Olympic Village by eight members of the Palestinian terrorist group Black September.

Nairobi. Capital of Kenya and site of U.S. Embassy bombed Aug. 7, 1998, by suicide bombers linked to bin Laden. U.S. Embassy in Dar es Salaam, Tanzania, was bombed at the same time. The two embassy attacks killed 301 and injured 5,000. United States retaliated with missile strikes on an abandoned training camp in Afghanistan and a pharmaceutical plant in Sudan, mistakenly thought to be a chemical weapons factory.

National Coordinator on Counterterrorism. National Security Council position. Retired Gen. Wayne Downing was appointed to the position.

National Pharmaceutical Stockpile. Vaccines and antidotes stored at Centers for Disease Control and Prevention in Atlanta, to protect against germ warfare.

Oklahoma City. Site of worst terrorist attack on U.S. soil before Sept. 11. Timothy McVeigh parked and detonated a truck loaded with explosive fertilizer in front of the Alfred P. Murrah Federal Building on April 19, 1995, killing 168 people, including 19 children. McVeigh, who was seeking to avenge the 1993 deaths of members of the Branch Davidian cult in Waco, Texas, was executed June 11. Accomplice Terry Nichols is serving a life term in federal prison and faces a possible death sentence in a pending trial on state murder charges.

Pan Am Flight 103. Airliner that blew up over Lockerbie, Scotland, in 1988, killing 270.

Pentagon. Headquarters of the U.S. Department of Defense. The five-sided, x-story building was completed in 1943. American Airlines Flight 77 crashed into the Pentagon Sept. 11, killing 189.

al Qaeda or al-Qaida. The terrorist network of bin Laden. It means "the Base" or "the Foundation."

Rahman. Omar Abdul Rahman, the "blind sheikh" with CIA ties, who was convicted as the mastermind of the 1993 bombing of the World Trade Center. Leader of Gamaa Islamiya.

Ressam. Ahmed Ressam was convicted of 1999 "millennium" plot to bomb Los Angeles International Airport during New Year's celebrations. He testified that bin Laden gave him $12,000 and told him to raise the rest of the money for his mission by robbing banks. Trained at camp in Afghanistan.

sarin. Nerve gas used in 1995 subway attack in Tokyo by Aum Shinrikyo cult. One of the most likely toxic chemicals to be used in a terrorist attack.

selling short. A technique in options trading that allows a party to profit from a decline in the market. Bin Laden's network is suspected of selling short before Sept. 11, to profit from the decline in airline and reinsurance stocks.

send a message. Cliché for the intended meaning of a terrorist attack or the response to a terrorist attack. Same as "make a statement."

smallpox. Deadly virus that was declared eradicated in 1979 by the World Health Organization. Vaccinations stopped, and even laboratory samples have been destroyed, though two research centers retain DNA fragments under tight security. Feared as a possible agent of bioterrorism.

state terrorism. Acts of terrorism by a government against its own people. Iraq has practiced state terrorism against the Kurds, just as Nazi Germany did against the Jews and other minorities and as Stalin did against various dissident groups.

state-sponsored terrorism. Acts carried out by non-government groups with funding, arms, intelligence or other direct or indirect help from a government. State Department lists seven nations as sponsors of terrorism: Cuba, Libya, Iran, Iraq, North Korea, Sudan and Syria.

terrorism. The use of force or threats to demoralize or intimidate a group of people for political reasons.

toxin. A toxin is a poison released by a living organism. Chemicals used in terrorism are not toxins.

TWA Flight 847. 1985 flight hijacked en route from Athens to Rome. Hijackers held the crew and most passengers hostage for 17 days, flying to Algiers and Beirut as they tried to negotiate for the release of prisoners held by the Israelis. The hijackers used airport cleaning crew to smuggle guns and grenades into the airplane's restroom.

United Airlines Flight 93. Crashed Sept. 11 in rural Pennsylvania. Hijacked en route from Newark to San Francisco. Some passengers apparently overpowered the hijackers, keeping them from hitting their intended target, possibly the U.S. Capitol. Believed to be the only Sept. 11 flight with four hijackers. Suspected hijackers were Saeed Alghamdi, Ahmed Alhaznawl, Ahmed Alnami and Ziad Jarrah.

United Airlines Flight 175. Crashed Sept. 11 into the south tower of the World Trade Center. Hijacked en route from Boston to Los Angeles. Suspected hijackers were Marwan al-Shehhl, Fayez Ahmed, Ahmed Alghamdi, Hamza Alghamdi and Mohand Alshehri.

USS Cole. Destroyer attacked Oct. 12, 2000, in Yemen's Aden Harbor by suicide bombers linked to bin Laden. Attack killed 17 and injured 39.

USS Sullivan. Target of failed January 2000 bombing attack in Yemen. The boat carrying explosives sank.

VX. Nerve gas feared as a possible agent in a chemical attack by terrorists.

World Trade Center. The seven-building financial complex was the target of a 1993 truck bombing that killed six people and injured more than 1,000. In the Sept. 11 attack, hijacked planes flew into both towers of the trade center, causing fires that caused the towers to collapse.

Yousef. Ramzi Yousef, Pakistani who planned the 1993 World Trade Center bombing. Also involved in failed plots to assassinate Pope John Paul II and President Bill Clinton and to bomb 11 U.S. airliners in flight on the same day in 1995. Other defendants in terrorism trials in the 1990s in the United States included Wadih el Hage, Mohamed al-Owhali and Khalfan Khamis Mohamed. Yousef was imprisoned with Unabomber Ted Kaczynski and Oklahoma City bomber Timothy McVeigh.

al-Zawahiri. Ayman al-Zawahiri, the leader of Egyptian Islamic Jihad, is believed to be hiding in Afghanistan with bin Laden and is viewed as perhaps the strategic leader of al Qaeda.