The Collaborative International Dictionary of English v.0.48:

nutty \nut"ty\, a.
   1. Abounding in nuts.
      [1913 Webster]

   2. Having a flavor like that of nuts; as, nutty wine.
      [1913 Webster]

   3. Crazy; insane; loony; batty; nuts. [slang]
      [PJC]

WordNet (r) 3.0 (2006):

nutty
    adj 1: having the flavor of nuts; "a nutty sherry" [syn:
           nutty, nutlike]
    2: 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:

126 Moby Thesaurus words for "nutty":
   abnormal, anomalous, apish, asinine, balmy, bananas, barmy, bats,
   batty, beany, bedlamite, befooled, beguiled, besotted, bonkers,
   brainless, buffoonish, buggy, bughouse, bugs, cockeyed, cracked,
   crackers, crank, crankish, cranky, crazed, crazy, credulous,
   crotchety, cuckoo, daffy, daft, dazed, deviant, deviative,
   different, dippy, divergent, dizzy, doting, dotty, dumb, eccentric,
   erratic, exceptional, fatuitous, fatuous, fey, flaky, flavorful,
   flavorous, flavorsome, flavory, flipped, fond, fool, foolheaded,
   foolish, freaked-out, freakish, fruitcakey, fruity, fuddled,
   full-bodied, full-flavored, funny, futile, gaga, goofy, gulled,
   gung ho, haywire, idiocratic, idiosyncratic, idiotic, imbecile,
   inane, inept, infatuated, insane, irregular, just plain nuts, keen,
   kinky, kooky, loony, loopy, mad, maggoty, maudlin, moronic, nuts,
   odd, oddball, off the hinges, off the track, off the wall,
   peculiar, potty, queer, quirky, rich, rich-flavored,
   round the bend, sappy, screwball, screwballs, screwy, senseless,
   sentimental, silly, singular, slaphappy, strange, stupid,
   thoughtless, twisted, unconventional, unnatural, wacky, warm, wet,
   whimsical, witless, zealous