September 11, 2001, the day on which four airliners were hijacked by terrorists for use in an attack on the U.S.: two were flown into the towers of the World Trade Center in Manhattan, one into the Pentagon, and the fourth crashed into a Pa. field
Origin of 9/11numeric representation of the month and the day
- /naɪn.wʌnˈwʌn/ is usually used for the telephone number 911 instead of the date.
- An event comparable to 9/11.
OriginSee also: 911
From the date September 11 written in numbers according the format used in the United States, which puts the month before the day.