Usually a girl, but can be a guy, who attaches herself to a guy or faux friends who have plenty of 420, just so she can suck on the bong and get high. The Bongsucking Leech has no money and contributes nothing to the party, so to speak, may not even be cute, but will sometimes perform sexual favors or do errands to work off some of the leech-ery in trade.
That pink-haired chick is such a bongsucking leech, she is just using him for his weed. She even admits it behind his back. Now I think she's even moved in with him and cleans his apartment and cooks just so she can get high now.