The Collaborative International Dictionary of English v.0.48:

Addle \Ad"dle\, v. t. & i. [imp. & p. p. Addled; p. pr. & vb.
   n. Addling.]
   To make addle; to grow addle; to muddle; as, he addled his
   brain. "Their eggs were addled." --Cowper.
   [1913 Webster]

WordNet (r) 3.0 (2006):

addled
    adj 1: (of eggs) no longer edible; "an addled egg"
    2: confused and vague; used especially of thinking;
       "muddleheaded ideas"; "your addled little brain"; "woolly
       thinking"; "woolly-headed ideas" [syn: addled, befuddled,
       muddled, muzzy, woolly, wooly, woolly-headed,
       wooly-minded]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "addled":
   addlebrained, addleheaded, addlepated, at a loss, baffled,
   bamboozled, beat, beclouded, beery, befuddled, bemused, besotted,
   blear-witted, blind drunk, buffaloed, cloudy, confounded,
   crapulent, crapulous, dazed, dizzy, drenched, drunk, drunken,
   far-gone, floored, flustered, fogged, foggy, fou, fuddlebrained,
   fuddled, full, gay, giddy, glorious, happy, hazy, in a dilemma,
   in a fog, in a muddle, in liquor, in suspense, inebriate,
   inebriated, inebrious, intoxicated, jolly, licked, maudlin, mellow,
   merry, misted, misty, muddled, muddleheaded, muddybrained, muzzy,
   mystified, nappy, nonplussed, on tenterhooks, perplexed, puzzled,
   puzzleheaded, reeling, scramblebrained, shikker, sodden, sotted,
   stuck, stumped, thrown, tiddly, tipsy, under the influence