Definitions
1.Proper nounSeptember 11, 2001; The date of the attacks on the World Trade Center and the Pentagon in the United States.
2.Proper nounThe attacks themselves.
3.NounSeptember 11, a date of the calender.
4.NounAn event comparable to the September 11 attacks.
5.NounA negative event that a person or a group of people have experienced whose impact is, hyperbolically, comparable to that of the September 11 attacks."This was my 9/11.; 9/11 for unfunny people"