(adj)
having or causing a whirling sensation; liable to falling; "had a dizzy spell"; "a dizzy pinnacle"; "had a headache and felt giddy"; "a giddy precipice"; "feeling woozy from the blow on his head"; "a vertiginous climb up the face of the cliff"
lacking seriousness; given to frivolity; "a dizzy blonde"; "light-headed teenagers"; "silly giggles"