The Collaborative International Dictionary of English v.0.48:

Addle-brain \Ad"dle-brain`\, Addle-head \Ad"dle-head`\,
Addle-pate \Ad"dle-pate\, n.
   A foolish or dull-witted fellow. [Colloq.]
   [1913 Webster] Addle-headed
   Addle-brained

Moby Thesaurus II by Grady Ward, 1.0:

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