9/11 9-membered • 90 · · · Info · Definitions · Characters · · 9/11 · · Text Common · · Script 4 · · Length 6 · · Syllables Definitions · · · (noun) the day in 2001 when Arab suicide bombers hijacked United States airliners and used them as bombs. Synonyms: 9-11, September 11, Sept. 11, Sep 11. · · Noun Definition 1 Characters · · / solidus U+002F 1 digit one U+0031 9 digit nine U+0039