September 11
Syllabification: (September 11)
(also 9/11)
Definition of September 11
- September 11, 2001. On this date, two hijacked commercial airliners were flown into the World Trade Center in New York City. A third hijacked airliner was crashed into the Pentagon, and a fourth went down in a field in Pennsylvania. The airliners were hijacked by Islamic fundamentalist terrorists believed to be involved with al-Qaeda.