What is “washout”?

Washout is a type of wing design where the angle of incidence reduces from the wing root to the wing tip. The angle of incidence is the angle between the longitudinal axis of the airplane and the chord line of the wing. Washout is like a warp in the wing. Washout makes it so the wing root reaches a higher angle of attack before the wing tip. This means the wing root will stall before the wing tip and thus creates more stability about the longitudinal axis; otherwise known as roll stability.