Princeton's WordNet

1. cockamamie, cockamamy, goofy, sappy, silly, wacky, whacky, zany(adj)

   ludicrous, foolish

   Synonyms:
   slaphappy, crackers, light-headed, ridiculous, round the bend, lightheaded, nutty, punch-drunk, dotty, featherbrained, sappy, kooky, daft, bats, empty-headed, clownish, airheaded, fruity, nuts, bonkers, clownlike, cracked, haywire, wacky, loco, kookie, buggy, zany, silly, goofy, pathetic, dizzy, batty, cockamamy, loony, barmy, cockamamie, buffoonish, around the bend, balmy, giddy, loopy, whacky

   Antonyms:
   wise, sane

2. 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(adj)

   informal or slang terms for mentally irregular

   Synonyms:
   crackers, nutlike, roughened, round the bend, bats, gaga, cockamamy, zesty, buggy, dotty, soft, wacky, kooky, daft, fruity, alligatored, zestful, kookie, nuts, sappy, bonkers, cracked, haywire, nutty, wrong(p), loco, wild, chapped, zany, silly, amiss(p), mild, awry(p), batty, crazy, loony, yeasty, barmy, cockamamie, goofy, around the bend, balmy, loopy, whacky

   Antonyms:
   wise, sane