Source : WordNet®

scatterbrained
     adj 1: lacking sense or discretion; "his rattlebrained crackpot
            ideas"; "how rattlepated I am! I've forgotten what I
            came for"- Glenway Westcott [syn: {rattlebrained}, {rattlepated},
             {scatty}]
     2: absent-mindedly irresponsible; "he said I was too flighty to
        be a good supervisor" [syn: {flighty}, {head-in-the-clouds}]