al-Qa ‧ e ‧ da BrE AmE , al-Qaida /æl kɑːˈiːdə, -ˈkaɪdə/
an Islamic organization formed in the 1980s by Arab men and women who were fighting in Afghanistan against the former Soviet Union, and led by Osama Bin Laden. After the Soviet soldiers left Afghanistan, al-Qaeda started a campaign of attacks against western countries, including the attack on New York City on September 11, 2001 when two planes flew into the World Trade Center and destroyed it. The US government announced a ‘war on terror’ and sent soldiers to Afghanistan to try and destroy al-Qaeda’s secret TRAINING CAMP s (=places where they teach people how to use guns and bombs etc) and to kill or catch its leaders.