See "Phalice Ring", "CockMonger", "Rim Job", "Dirty Harry", "Repetition", "Profanity", "Fart Jokes"

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