9/11 Definition

nīnēlevən, nīnilevən
noun
September 11, 2001, the date on which two hijacked airliners were flown into the World Trade Center in New York City and another into the Pentagon. A fourth hijacked airliner crashed in open land in Pennsylvania.
American Heritage
An event comparable to 9/11.
Wiktionary
Synonyms:
pronoun

The date of the attack on the Twin Towers and the Pentagon in the USA, September 11th, 2001.

Wiktionary
The attack itself.
Wiktionary
symbol

The cardinal number nine.

Wiktionary

Other Word Forms of 9/11

Noun

Singular:
9/11
Plural:
9-11s

Origin of 9/11

  • From the date September 11 written in numbers according the format used in the United States, which puts the month before the day.

    From Wiktionary