One who is apt to behave in a stupid, silly, or scatterbrained manner. Did I really forget my wallet at home? I can be such a ditz sometimes.Oh, she's a ditz all right—she just said that two plus two is seven.
ditz
and ditzo (dɪts(o))n. a giddy, absent-minded person. I’m getting to be such a ditz! What a ditzo!