When you're at a wild party, or in any situation and you catch a guy hooking up with a passed-out drunk girl who is way younger than him, preferrably underage, you pull him off of her and repeatedly kick him in the face.

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