antiknock

[an-tee-nok, an-tahy-, an-tee-nok, an-tahy-]
adjective
  1. noting or pertaining to a substance, as tetraethyllead or ferrocene, used as a fuel additive for an internal-combustion engine to eliminate or minimize knock.
noun
  1. such a substance added to fuel in an internal-combustion engine.

Origin of antiknock

First recorded in 1920–25; anti- + knock
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for antiknock

antiknock

noun
  1. a compound, such as lead tetraethyl, added to petrol to reduce knocking in the engine
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