or 9-11

[ nahyn-i-lev-uh n ]
/ ˈnaɪn ɪˈlɛv ən /

September 11, 2001: the day on which Islamic terrorists, believed to be part of the Al-Qaeda network, hijacked four commercial airplanes and crashed two of them into the World Trade Center in New York City and a third one into the Pentagon in Virginia: the fourth plane crashed into a field in rural Pennsylvania.
Also called nine-elev·en.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019