the opposite of a "cock-blocker", it's when a girl is denied advances by another person stepping in and talking to the party of interest. said person can be either male or female, as long as they interfere with the possibility of a hook-up
"Ladybird was such a cunt clogger tonight... I couldn't get any action."
"I just got cunt-clogged by that Ladybird, what the ef!"