The opposite of blue balls ...This is What happens When the pussy is so good she drains both balls so much that they hurt and feel like empty shells that are going to implode

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