The Collaborative International Dictionary of English v.0.48:

Muddlehead \Mud"dle*head`\, n.
   A stupid person; a blunderer. [Colloq.] --C. Reade. --
   Mud"dle-head`ed, a. [Colloq.] --Dickens.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "muddleheaded":
   addlebrained, addled, addleheaded, addlepated, beclouded,
   befuddled, blear-witted, cloudy, dizzy, fogged, foggy,
   fuddlebrained, fuddled, hazy, in a fog, in a muddle, misted, misty,
   muddled, muddybrained, muzzy, puzzleheaded, scramblebrained