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O-ring

[oh-ring]
noun
  1. a ring of pliable material, as rubber or neoprene, used as a gasket: the failure of an O-ring caused the explosion that destroyed the space shuttle Challenger in 1986.

Origin of O-ring

First recorded in 1945–50
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for o-ring

O-ring

noun
  1. a rubber ring used in machinery as a seal against oil, air, etc
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