Definition
A vibration or shaking of the airframe caused by turbulent, separated airflow striking the wings, tail, or fuselage. In slow flight and stall situations, buffet is an aerodynamic warning that the wing is approaching its critical angle of attack and airflow is beginning to break away from the upper wing surface.
Plain English
A shudder or shaking you feel through the airframe when the air stops flowing smoothly over the wing. It's an early physical warning that the airplane is getting close to a stall.
Context Anchor
Seen in slow flight and stall awareness training, when a pilot is learning to recognize the physical signs that the wing is close to losing smooth airflow.
Derivation
From the Old French 'buffet,' meaning a blow or strike. The aviation use keeps that sense -- the airframe is being struck repeatedly by disturbed, swirling air rather than gliding through smooth airflow.
Why Pilots Care
It acts as a natural, built-in warning of an approaching stall, giving the pilot time to reduce angle of attack before a full stall occurs.
Grounding Statement
In the cockpit, aircraft buffet may feel like a light shaking through the seat, controls, or airframe as the airplane approaches the edge of smooth flight.
Intuition Check
Do not read “buffet” as the everyday word for a meal, or as any random vibration. In aviation, aircraft buffet means shaking caused by disturbed airflow around the airplane.
Example Sentence 1
As the airspeed decayed during the slow flight maneuver, the student felt the first light buffet and immediately reduced back pressure on the yoke.
Example Sentence 2
During an approach to landing, recognizing aircraft buffet allowed the pilot to correct pitch attitude before a stall developed.