The act of inserting a small furry animal into one's own (or one's partner's) anal cavity.

A jack off buddy (from 'cum' /'come', meaning 'semen', and 'companion'); a friend that you get together with for sessions of solo or mutual masturbation
Variant of: cumpanion (from 'companion' & 'cum'); jack off buddy & wank bud & JO buddy
Similar to: fuck buddy

when you take the lint from your belly button and put it into someone else's belly button. You do this action back and forth between you and that person's belly button lint.