Slip In Butt Share definition Flag When your doing a girl from behind and you "accedently" slip into her butt. Afterwards tell her to walk it off. Tom gave Denise the slip in butt last night, now hes sleeping on the couch for the next week. Slip In Butt by asexybum December 2, 2007 0 0 Get merch Get the Slip In Butt mug. Buy Now — $32.95 See more merch