In the event of a cock block where one male cock blocks another male, the blocking male may attempt to steal the opposing male's target and swap the blocked cock with his.
This is usually done out of spite of the blocked male.
Charlie: I totally cock blocked Michael the other day.
Kevin: You should have gone further and cock swapped him.
Charlie: Yeah I should have.......... And... I SHALL!
Whereas 'Cockblocking' is the act of preventing someone from getting laid, the act of 'Cockswapping' is when the swapper purposely blocks the sexual attempts of a third party, only to move in after they've ruined everything for their own personal gain.
A cockswapper knowingly uses lies, money, or any other means to steal a potential sexual partner from someone else.
A cockswap can be performed by men and women, however is mostly used as a term by men, as women usually just call the offending party a 'slut'.
"I was talking to this girl, and then Bob told me she was ugly, and I could do better. Then, later that night, he cockswapped, and told her I called her ugly, and slept with her. What a prick!"
Cock swap is when one party cock blocks, only to replace said lost cock with an alternative one.
Gay guy A is about to hook up with gay guy B, when gay guy C cock swaps causing guy B to leave.