DNO stands for Dudes Night Out. These occur once every 2-3 months. They usually occur when some bros just want to chill on a Sunday night. The DNO can start with a few beers and will end with what ever the best movie in theaters is. DNO's can not involve women in anyway what so ever.
Dude 1: Yo you know how we tried to have a DNO this weekend.
Dude 2: Ya why was it called off?
Dude 1: Because someone thought they would invite a chick.
Dude 2: Wow he would, I can't believe he ruined it.