Synonyms of mindless

1 Syllable
out, rash
2 Syllables
brutish, silly, bruter, simple, foolish, fatuous, witless, moony, thoughtless, stupid, mooning, heedless, nescient, brainless, reckless, nutsy
3 Syllables
unstudious, stupidest, ignorant, off-the-wall, inanest, forgetful, regardless, nitwitted, spaced-out, neglectful, senseless, inane, idiotic, unmindful, unthinking, moronic, obtuse, thick-headed, careless, negligent, gratuitous, psychiatric, daydreaming
4 Syllables
lamebrained, irrational, imbecilic, unscholarly, nonobservant, uninstructed, unreasoning, unaware, cockamamie, harebrained, asinine, cockamamy
5 Syllables
unintelligent, irrespective, unknowledgeable, unreflective, anencephalic, inattentive, unintellectual, anencephalous, pococurante
7 Syllables
overventuresome