A would be friend, or relative that comes to spend one night on your couch and then never leaves. They eat all of the food in your fridge and use up all of your toilet paper. They have no respect for you or your mates.
Dude, you gotta talk to your bro. He's been low baggin' here since last October. He's gotta go, man!
1) sketchily secluding yourself from the people you know
2) being a hermit (don't confuse this with being a hobbit- that is something different- see Lord of the Rings)
3) being anti-social
1) staying in your room, alone, with the door closed on a saturday night (note: this does not mean closing the door and drinking with your roommate and a couple friends or whoever knocks...)
2) taking a many-mile walk alone (note-this walk is not for exorcise or running errands; it is for purposely getting away from the people you know....though, yes, you are technically out in the public)