Synonyms and related words :
blank, brainless, dizzy, empty, empty-headed, empty-minded, empty-pated, empty-skulled, featherbrained, featherheaded, flighty, fluttery, frivolous, gaga, giddy, giddy-brained, giddy-headed, giddy-pated, giddy-witted, harebrain, harebrained, hollow, inane, jejune, rattleheaded, rattlepated, scatterbrained, scramblebrained, shatterbrained, silly, skittish, thoughtless, vacant, vacuous, vapid, witless