An all encompassing term for initiating sexual activity in an upstairs area, typically, but not limited to, a bedroom. It is a conjunction of "Let's go up." Most often used when in a hurry to start slappin' parts, and too lazy to actually pronounce the whole phrase.

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