To masturebate in someone else's house; or someone else's property. In many countries this is a sign of deepest gratitude to your host, but it is best advised to check with a local before starting up your engines. This is different from public masturbation.

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