September 11
Definition of September 11
- the date of an attack in 2001 in which two airliners were flown directly into the World Trade Center in New York, causing the complete collapse of the twin towers, and a third airliner was flown into the Pentagon, causing a five-storey section of the building to collapse; a fourth airliner, believed also to have been targeted on Washington, was brought to the ground in Pennsylvania as a result of what is thought to be passenger intervention. The airliners were hijacked by Islamic fundamentalist terrorists believed to be involved with al-Qaeda. Also called 9/11.