This is the abbreviation for Butt To Mouth Transfer. Most commonly seen only in porno films. This Is where the guy pulls his cock out the woman or other man's ass and then the former reciever slobs that knob clean as a whistle. Side note, guys if you find one who does this without batting an eye lash, she is a keeper!
(Nerd 1) Oh my God dude did you see that video where she totally BTMTed that guy? (Nerd 2) Yeah that had to be the most hilarious thing I saw all week.