A person, who usually isn't very intelligent, who will not shut up. It's typically a cover for their own inferiority.

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

When someone won't STFU and keeps blabbering their inane chatter.

constant talk with no information value. unstoppable talking. saying alot but saying nothing at all, not to be confused with saying alot by saying nothing at all. meaningless and unstoppable talk. drug-induced chatter. politics. barf.

Talking too much, usually about something unimportant.

when one needs to take a shit but it comes out from the wrong end.

When someone won't STFU, and he doesn't realize that everyone stopped listening a long time ago.