Da Fightin Irish is a sexual act when someone gives fellatio with one hand on the shaft, and the other going under between the legs and fisting the mans anus, which ends up looking like the Fighting Irish college mascot.
Oh man, I came home early the other day and walked in on my flatmate Ed giving Mike Da Fightin Irish! I haven't been back yet!
by St_patrick-Sledgehammer7569 January 3, 2019