The Collaborative International Dictionary of English v.0.48:

Redfish \Red"fish`\ (r[e^]d"f[i^]sh`), n. (Zool.)
   (a) The blueback salmon of the North Pacific; -- called also
       nerka. See Blueback
   (b) .
   (b) The rosefish.
   (c) A large California labroid food fish (Trochocopus
       pulcher); -- called also fathead.
   (d) The red bass, red drum, or drumfish. See the Note under
       Drumfish.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fathead \Fat"head`\, n. (Zool.)
   (a) A cyprinoid fish of the Mississippi valley (Pimephales
       promelas); -- called also black-headed minnow.
   (b) A labroid food fish of California; the redfish.
       [1913 Webster]

WordNet (r) 3.0 (2006):

fathead
    n 1: a man who is a stupid incompetent fool [syn: fathead,
         goof, goofball, bozo, jackass, goose, cuckoo,
         twat, zany]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "fathead":
   addlebrain, addlehead, addlepate, beefhead, blockhead, blubberhead,
   blunderhead, bonehead, boob, booby, bufflehead, cabbagehead,
   chowderhead, chucklehead, chump, clodhead, clodpate, clodpoll,
   dolt, dolthead, dullhead, dumbhead, dunderhead, dunderpate, goof,
   goon, jolterhead, jughead, knucklehead, lunkhead, meathead,
   muddlehead, mushhead, muttonhead, noodlehead, numskull, oaf,
   peabrain, pinbrain, pinhead, puddinghead, pumpkin head, puzzlehead,
   stupidhead, thickhead, thickskull, tottyhead