A person who is a combination of stupid, lazy, and otherwise useless to the point that they have no purpose other than to breathe everyone else's air.
In college, I had this roomate who flunked out of school. He continued to live with us even though he didn't pay for anything and just watched Columbo reruns all day. Eventually, I had to kick that oxygen user out.
by Rev. Pasternack July 12, 2006