Synonyms and related words :
birdbrain, crackbrain, crank, cuckoo, ding-a-ling, featherbrain, featherhead, flibbertigibbet, giddybrain, giddyhead, kook, lunatic, nut, rattlebrain, rattlehead, rattlepate, scatterbrain, scatterbrains, screwball, shallowbrain, shallowpate, shatterbrain