scatterbrained

noun

1. a person incapable of serious, connected thought.

adjective

1. exhibiting or characterized by lack of serious thought or concentration; disorganized; silly

noun

1. a person who is incapable of serious thought or concentration

n.also scatter-brain, “thoughtless, giddy person, one incapable of serious, connected thought,” 1764 (scatter-brained), from scatter (v.) + brain (n.). Related: Scatterbrained. Cf. scatter-good “spendthrift.”