piston ring

noun

a metallic ring, usually one of a series, and split so as to be expansible, placed around a piston in order to maintain a tight fit, as inside the cylinder of an engine.

Origin of piston ring

First recorded in 1865–70

Also called packing ring, ring.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for piston ring

Historical Examples of piston ring

This was probably done to reduce vibration and the problem of piston-ring sealing.
The First Airplane Diesel Engine: Packard Model DR-980 of 1928
Robert B. Meyer

British Dictionary definitions for piston ring

piston ring

noun

a split ring, usually made of cast iron, that fits into a groove on the rim of a piston to provide a spring-loaded seal against the cylinder wall

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012