Plain English Meaning

The propeller has small weights attached to it. As the propeller spins, those weights are flung outward, and that outward pull is used to twist the blades into a steeper angle on their own — without needing oil pressure to do it.

Full Definition

Fitted with weights positioned so that centrifugal force, generated as the propeller rotates, acts to move the propeller blades toward a higher pitch (coarser) angle. On feathering propellers, these counterweights provide the force that drives the blades toward the feathered position when oil pressure is reduced or lost.

Context Anchor

Seen in descriptions of feathering propellers, especially when explaining how blade angle changes after oil pressure drops or an engine is shut down.

Derivation

From 'counter-' (against, opposing) plus '.' A is a weight placed to oppose or another force. On a propeller, the counterweights oppose the forces that would otherwise twist the blades toward , so when something fails, the blades move the other way — toward coarse pitch or .