WordNet (r) 3.0 (2006):

pinhead
    n 1: an ignorant or foolish person [syn: dumbbell, dummy,
         dope, boob, booby, pinhead]
    2: the head of a pin

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "pinhead":
   addlebrain, addlehead, addlepate, beefhead, beetleheaded,
   blockhead, blockheaded, blubberhead, blunderhead, bonehead,
   bufflehead, cabbagehead, cap, capsheaf, caput, chowderhead,
   chucklehead, chuckleheaded, clodhead, clodpate, clodpoll, cluck,
   crest, crown, crumb, dense, dimwit, dolthead, doltish, dot, drop,
   droplet, dullhead, dumb cluck, dumbhead, dunderhead, dunderpate,
   fathead, fatheaded, featherweight, fleck, flyspeck, gnat, grain,
   head, heading, headpiece, iota, jolterhead, jot, jughead,
   knucklehead, lackwit, lunkhead, meathead, microbe, microorganism,
   midge, minim, minutia, minutiae, mite, mote, muddlehead, mushhead,
   muttonhead, nitwit, noodlehead, numskull, particle, peabrain,
   pinbrain, pinpoint, point, puddinghead, pumpkin head, puzzlehead,
   scrap, simp, snip, snippet, speck, stupidhead, thickhead,
   thickskull, tittle, topknot, tottyhead, vanishing point