To position the feet of (a person) while sitting, lying down, or reclining so that the knees are elevated at a higher level.
To manually start the engine of a propeller-driven aircraft with no electric starter by pulling vigorously on one of the propeller blades using the hands, so that the propeller can catch ignition.
Origin
From Middle English proppe, from Middle Dutch proppe. Compare Middle Low German proppe, German Pfropfen, Danish prop.