An acronym for a total random boner moment. It is classified by one obtaining a boner when one typically wouldn't have a boner.
Person 1- I just puked in the break room toilet (at work). Then decided to fap.
Person 2- WAT! I can't believe you had the energy to fap after vomiting. Did you force it?
Person 1- total random boner moment
Person 2- gotta love TRBM's.