butthole grabber 

Someone who sneakily slips a hand, finger, or object into someone's anus and carefully grabs it

" Hey , get your finger out of my butt, you butthole grabber"

butthole grabber by Kaylaykay August 23, 2017

Ghost butthole grabber 

When you stealthily swim up on someone in the pool and you poke them in the butthole and then say "ghost butthole grabber... yeahhh"

I just got poked by that "ghost butthole grabber"

Ghost butthole grabber by Hizzlebadizzle March 31, 2022