Definition 1 of 2
Definition
A reciprocating internal combustion engine in which fuel is burned inside cylinders to drive pistons up and down. The pistons are connected to a crankshaft that converts their reciprocating motion into rotary motion, which turns the propeller. Piston engines used in light aircraft are typically four-stroke and air-cooled, and run on aviation gasoline (avgas).
Plain English
An engine that burns fuel inside enclosed cylinders to push pistons back and forth. That motion is turned into spinning motion to drive the propeller. It is the same basic type of engine found in most cars, just adapted for aircraft use.
Context Anchor
Seen in aircraft engine descriptions, preflight inspections, engine operation, and discussions of power settings in many training airplanes.
Derivation
From the Italian 'pistone', meaning a large pestle, the same root as 'pistol'. The piston is the part that pounds up and down inside the cylinder, the way a pestle pounds inside a mortar. Knowing this helps picture what the moving part is actually doing.
Why Pilots Care
Pilots must understand piston engines to set proper power, manage cylinder temperatures, and handle engine failures safely in general aviation aircraft.
Analogy
A piston engine is a little like legs pushing bicycle pedals. The push is back-and-forth, but the machine turns that motion into rotation.
Intuition Check
A piston engine is not the same as every aircraft engine. It specifically uses pistons moving inside cylinders; turbine engines make power in a different way.
Example Sentence 1
The Cessna 172 is powered by a four-cylinder piston engine that drives a fixed-pitch propeller.
Example Sentence 2
During the engine failure drill, the instructor emphasized keeping the piston engine within its normal operating temperature range.