A cum tart is a sexually promiscuous guy or girl that seeks out cum, but in a selective manner. In a sense a cum tart is a slut that likes to think they have morals.
"But Jasper you've already fuck everyone here you little cum tart, if you dont find a new stomping ground soon people are gonna think your a dirty fucking cum-slut that'll just do anything with a hole!"
"She was acting like such a cum tart but we all knew she didn't care who or what fucked her!" "Are you still talking about Jasper?" "Yeh"