Etymologically speaking, a person who mooches weed.
An individual who has the monetary means of obtaining marijuana, but who manipulates friendships in order to "smoke out" at no cost (other than his credibility). This person will usually show up shortly before a cannibus-smoking session and leave shortly after having his fill of the "devil's lettuce". Said person often "bogarts" as well.
Nostradamus: Alright let's blaze up this dunk-ass nugget
Imhotep: Hells yeah, son!
Billy: Hey, can I hit that too y'all?
Nostradamus: Get your own shit, you fucking weech!