Definition of bumming:
(n) :
(colloquial, sometimes derogatory) A homeless person, usually a man.
(n) :
(colloquial, sometimes derogatory) A lazy, incompetent, or annoying person, usually a man.
(v) :
(intransitive, colloquial) To stay idle and unproductive, like a hobo or vagabond.
(v) :
(transitive, colloquial) To ask someone to give one (something) for free; to beg for something.
(n) :
(colloquial, sports) A player or racer who often performs poorly.
(n) :
(informal or childish, chiefly Commonwealth) The buttocks.