The Oxford Thesaurus An A-Z Dictionary of Synonyms - flighty adj.

1) fickle, frivolous, inconstant, capricious, fanciful, changeable, variable, mercurial, skittish, volatile, unstable, unsteady, giddy, wild: These flighty girls never stay in a job more than a month. 2) irresponsible, light-headed, rattle-brained, silly, hare-brained, dizzy, crazy, mad, reckless, thoughtless, Colloq nutty, screwy, dotty, dippy: It was flighty of Caroline to pour the brandy into the well.