Tattoo of Greek letters, crest, or other Fraternity symbol on ones body.
What an idiot, that frat tat won't rub off!
by Tree_PiKA September 22, 2009
A Frat Tat is when you put roofies and a young lady's drink, have sex with her and before she awakens from her roofie induced slumber, draw all over her face with a magic marker.
I'm not sure if I had a good time but I did wake up with a frat tat so how bad could it have been?
by Necronious January 15, 2012