Referring to late night sex or masturbation. Usually includes the use of (but not limited to) dildos, strap-ons, and anal beads. May be gay or straight sex and can include any number of people.

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