9/11 n. September 11, 2001 the day when two airplanes hijacked by Islamic terrorists were deliberately crashed into the "twin towers" (the two 110-storey skyscrapers of the World Trade Center) in New York City, causing those buildings to collapse and much other damage in the nearby area. Another plane was crashed into the Pentagon near Washington. In total, the attacks caused nearly 3,000 deaths. This was the worst incident of terrorism inside the United States to date. The abbreviated date 9/11 is now taken to refer to that specific day and the terrorist incidents that occured that day. It is used especially in the phrase "the events of 9/11".
Collaborative International Dictionary of English 0.48