The Collaborative International Dictionary of English v.0.48:

Chum \Chum\, n.
   Chopped pieces of fish used as bait. [U. S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Chum \Chum\ (ch[u^]m), n. [Perh. a contraction fr. comrade or
   chamber fellow: cf. also AS. cuma a comer, guest.]
   A roommate, especially in a college or university; an old and
   intimate friend.
   [1913 Webster]

   New chum, a recent immigrant. [Australia]
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Chum \Chum\, v. i. [imp. p. p. Chummed; p. pr. & vb. n.
   Chumming.]
   To occupy a chamber with another; as, to chum together at
   college. [U. S.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

chum
    n 1: a close friend who accompanies his buddies in their
         activities [syn: buddy, brother, chum, crony,
         pal, sidekick]
    2: bait consisting of chopped fish and fish oils that are dumped
       overboard to attract fish
    3: a large Pacific salmon with small spots on its back; an
       important food fish [syn: chum salmon, chum,
       Oncorhynchus keta]