A male who lives with his girlfriend without paying rent.
Rent and bills are paid by the girlfriend, the cocklodger relies on the fact that the couple are shagging to continue his residency.
Yeah, that guy Jim doesn't pay Rebeccarent to live in her flat, he's a cocklodger.
A girl (or guy) who's always got one hand holding a dude's cock and the other digging in his pockets. They are completely unable to sustain themselves on their own and are closer to being parasites than human beings.
Person 1: Whatever happened to that hot chick from high school?
Person 2: She realized that she couldn't do anything else useful for society so she just became a cockholder. I see her at the bar with a different dude every night, and he's always buying....