Plain English Meaning

Small internal pins that stop the propeller blades from turning edge-on to the wind on their own when the engine is shut off on the ground. They lock automatically when the prop slows down and release automatically once it spins fast enough.

Full Definition

Spring-loaded pins inside a feathering propeller hub that mechanically prevent the propeller blades from drifting into the feathered position when the engine is shut down on the ground. They are held disengaged in flight by centrifugal force acting on the pins as the propeller rotates above a set RPM, and they re-engage to lock the blades out of feather as RPM falls below that threshold during shutdown.