The Collaborative International Dictionary of English v.0.48:

Daft \Daft\ (d[.a]ft), a. [OE. daft, deft, deft, stupid; prob.
   the same word as E. deft. See Deft.]
   1. Stupid; foolish; idiotic; also, delirious; insane; as, he
      has gone daft.
      [1913 Webster]

            Let us think no more of this daft business --Sir W.
                                                  Scott.
      [1913 Webster]

   2. Gay; playful; frolicsome. [Scot.] --Jamieson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

daft
    adj 1: informal or slang terms for mentally irregular; "it used
           to drive my husband balmy" [syn: balmy, barmy,
           bats, batty, bonkers, buggy, cracked,
           crackers, daft, dotty, fruity, haywire,
           kooky, kookie, loco, loony, loopy, nuts,
           nutty, round the bend, around the bend, wacky,
           whacky]

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "daft":
   abnormal, absurd, apish, asinine, batty, bedlamite, befooled,
   beguiled, bereft of reason, besotted, boneheaded, brainless,
   brainsick, buffoonish, cockamamie, cockeyed, crackbrained, cracked,
   crazed, crazy, crazy about, credulous, cretinous, daffy, dazed,
   deluded, demented, deprived of reason, deranged, dim-witted,
   disoriented, distraught, dizzy, dopey, doting, dumb, fat-witted,
   fatuitous, fatuous, flaky, flighty, fond, fool, foolheaded,
   foolish, fuddled, futile, gaga, giddy, goofy, gulled, hallucinated,
   idiotic, imbecile, imbecilic, inane, inept, infatuated,
   infatuated with, insane, irrational, kooky, loco, loony, lunatic,
   mad, mad about, maddened, manic, maudlin, mazed, mental,
   mentally deficient, meshuggah, moon-struck, moronic, non compos,
   non compos mentis, nonsensical, not all there, not right,
   nuts about, nutty, obtuse, odd, of unsound mind, off, psycho,
   queer, reasonless, ridiculous, sappy, screwy, senseless,
   sentimental, sick, silly, slow-witted, stark-mad,
   stark-staring mad, strange, stupid, sweet on, tetched, thoughtless,
   touched, unbalanced, unhinged, unsane, unsettled, unsound, wacky,
   wandering, weak-minded, wet, witless