The Collaborative International Dictionary of English v.0.48:

Chump \Chump\ (ch[u^]mp), n. [Cf. Icel. kumbr a chopping, E.
   chop.]
   1. A short, thick, heavy piece of wood. --Morton.
      [1913 Webster]

   2. a stupid person; a fool; a dolt; also, a dupe.
      [PJC]

   Chump end, the thick end; as, the chump end of a joint of
      meat. --Dickens.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chump
    n 1: a person who is gullible and easy to take advantage of
         [syn: chump, fool, gull, mark, patsy, fall guy,
         sucker, soft touch, mug]