While frantically driving around in a vehicle with a partner and in need of a spot to engage in sexual activity with no options, decide to park somewhere to get the job done in desperate, horny situations.

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