I'm guessing it's simply a person that leeches off of you repeatedly and happens to also be something of a "fuck".
Could also be a 20+ year old man with no real healthy libido or incentive really to have his own life. Lives with enabling mother. He probably has Xbox pajama pants to go with the closest thing to a girlfriend he has; his Xbox. With no job and no real future he'll probably end up being a plumber or a hobo...or a couch potato...at his mother's house of course. Has probably watched Hentai multiple times.
May have some strange religious beliefs too.
Rob is such a Moochfuck, he doesn't have a job and all he does is play Xbox at his mom's house...and I'm pretty sure he still lives there too.