noun, noun which may take the genitive case particle 'no'
Slang reversal of キチガイ; derogatory and offensive. Used to refer to someone acting crazy or to the state of madness itself.
See also: キチガイ
あいつ、急に叫び出してガイキチかと思った。
He suddenly started screaming and I thought he was a madman.
そんなガイキチな行動はやめろ。
Stop that crazy behavior.