Definition
A rotating device with two or more shaped blades, driven by the engine, that produces thrust by accelerating a mass of air rearward. Each blade is an airfoil set at an angle to its plane of rotation, so as the propeller turns, the blades pull (or push) the aircraft through the air.
Plain English
The spinning set of blades on the front (or back) of many aircraft. The engine turns it, and as it spins it grabs air and throws it backward, which pulls the aircraft forward.
Context Anchor
You encounter the propeller during preflight inspection, engine start, takeoff, climb, cruise, and any discussion of aircraft performance or engine operation.
Derivation
From the Latin propellere, meaning 'to drive forward' (pro- 'forward' + pellere 'to push or drive'). The name describes exactly what it does: it drives the aircraft forward through the air.
Why Pilots Care
The propeller is the main source of thrust on most piston-powered aircraft; its condition, pitch, and RPM directly affect takeoff performance, climb rate, and fuel efficiency.
Analogy
A propeller is like a powerful fan with a different purpose: instead of just blowing air across a room, it creates the force that moves the aircraft.
Intuition Check
Do not think of a propeller as only a flat paddle spinning in the air. Its blades are shaped to create aerodynamic force, much like wings do, while they rotate.
Example Sentence 1
During the preflight inspection, the pilot ran a hand along each propeller blade to check for nicks or cracks.
Example Sentence 2
During the climb the pilot adjusted propeller RPM to maintain the recommended setting for best rate of climb.