The Toilet.

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

Realtors often mistakenly refer to this as a "toilet room". It's the small enclosed space inside a larger bathroom where the throne is located. It has to have a door, which is closed during #2 operations, but not necessarily on #1 operations.