thick-headed

from The Collaborative International Dictionary of English v.0.48

Thick-headed \Thick"-head`ed\, a.
   Having a thick skull; stupid.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

30 Moby Thesaurus words for "thickheaded":
      beetleheaded, blockheaded, blunt, blunt-witted, chuckleheaded, dim,
      dim-witted, dopey, dull, dull of mind, dull-headed, dull-pated,
      dull-witted, fat-witted, fatheaded, gross-headed, heavy,
      hebetudinous, numskulled, obtuse, slow, slow-witted, sluggish,
      thick, thick-brained, thick-headed, thick-pated, thick-witted,
      thickskulled, wooden