crackbrain

[ krak-breyn ]
/ ˈkrækˌbreɪn /

noun

a foolish, senseless, or insane person.

Origin of crackbrain

First recorded in 1560–70; crack(ed) + brain

British Dictionary definitions for crackbrain

crackbrain
/ (ˈkrækˌbreɪn) /

noun

a person who is insane