Synonyms of birdbrained

2 Syllables

silly, numbskull, dingdong, fatuous, vacuous, witless, dizzy, thoughtless, gorked, stupid, flighty, giddy, flightier, nescient, madcap, dumdum, flightiest

3 Syllables

frivolous, unstudious, ignorant, forgetful, half-baked, retardo, idiotic, slaphappy, retarded, careless, squirrelly

4 Syllables

illogical, irrational, empty-headed, featherbrained, unscholarly, uninstructed, harebrained, cockamamy, scatterbrained

5 Syllables

underachieving, unknowledgeable, irresponsible, unintellectual, inattentive