b-tub
It stands for....Bitch Tittiefeal Undo Bra. The b-tubber pokes the victims ribs so they laugh/squeal/jump etc.They then grab their boobs.Then they atempt to undo their bra.People see who can do it the fastest for fun.
guy1: omg i just b-tubbed that girl.
guy2: your screwed.
guy2: your screwed.