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. 2019
Examples from the Web for 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
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