1. Lost in thought; showing preoccupation
   "the scatty glancing quality of a hyperactive but unfocused intelligence";
   - absent, absentminded, abstracted
    
2. Lacking sense or discretion
   "his scatty crackpot ideas";
   - rattlebrained, rattlepated, scatterbrained

Derived forms: scattiest, scattier

See also: daft [Brit, informal], dumb, foolish, imbecile, imbecilic, inattentive, stupid, unattentive [rare]