When a couple are both upset and emotions are high and they are both full of tears, they fuck. They do this because they are both upset, not to make them feel better.
Me and Suzie had a sad-fuck the other night when our dog was put down.
1. A person who is universally considered to be both a complete prick and a pitiful loser. Not usually shouted, more often delivered with controlled disdain.
2. Less commonly used to describe unhappy coitus.
e.g. ‘You are one sad-fuck.’