9/11
Definition
The coordinated terrorist attacks carried out by al-Qaeda on September 11, 2001, targeting the World Trade Center in New York City, the Pentagon in Arlington, Virginia, and a failed attempt that crashed in Shanksville, Pennsylvania, resulting in nearly 3,000 deaths.
A shorthand reference to the aforementioned events, often used in discussions of national security, geopolitics, counterterrorism, and cultural memory in the United States and globally.
Informally, the date September 11th, especially in American English date notation (month/day), evoking themes of resilience, remembrance, and conspiracy theories.
Examples
9/11 turned 'board meeting' into the understatement of the century.
After 9/11, my fear of heights got a serious upgrade – thanks, gravity.
He claims 9/11 was an inside job, but his real conspiracy is how he burns toast every morning.
On the anniversary of 9/11, we remember with bagels and a vow to question everything except brunch plans.