Plain English Meaning
A small flap on the back edge of a stabilator that moves the same way the stabilator moves. It deliberately makes the controls feel heavier so the pilot does not move the stabilator too far too easily.
Full Definition
A small auxiliary control surface attached to the trailing edge of a stabilator that moves in the same direction as the stabilator. Its purpose is to increase the control force the pilot feels and to prevent the stabilator from being over-controlled. It also functions as a trim tab when adjusted by the pilot.
Context Anchor
Seen during tail inspection, control-surface rigging, and discussions of stabilator-equipped aircraft.
Derivation
The name combines 'anti' (against) with 'servo' (a device that assists movement). A normal servo tab helps the pilot move a control surface. An antiservo tab does the opposite — it works against easy movement, adding resistance so the controls do not feel too light.
Why Pilots Care
Prevents over-sensitive pitch response on aircraft that use a stabilator instead of a fixed horizontal stabilizer and elevator.
Intuition Check
Do not think of “antiservo” as meaning the tab stops movement. It still moves; it moves in a way that adds control feel instead of helping the surface move more easily.
Example Sentence 1
During the preflight inspection, the pilot checked that the antiservo tab on the stabilator moved freely and was secure.
Example Sentence 2
With the antiservo tab installed, the pilot felt increased resistance when pulling the nose up, improving pitch stability at cruise speed.