When a girl is giving you a blow job in a hot tub or pool, you hold her down below the water until you cum in her mouth as she drowns. Then call the lifeguard over to give her mouth to mouth and laugh as he swallows your cum.

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