A precisely machined cylindrical component that slides linearly within a cylinder bore. In an engine, it captures the expanding force of combusting gases and transfers it to the crankshaft via a connecting rod. In pumps and compressors, an external force drives it to compress or displace a fluid. It is usually fitted with rings to seal the gap against the cylinder wall.
Heard on the job
We need to pull the head and inspect the cylinder because cylinder three has a cracked piston.
Insider tip
Scoring on the skirt usually indicates poor lubrication or overheating, not just normal wear.