See also: anti-knock English Alternative forms anti-knock Etymology From anti- + knock. Pronunciation Audio (US):(file) Adjective antiknock (not comparable) Of an additive added to petroleum/gasoline to reduce the occurrence of engine knock. Translations reducing the occurrence of engine knock Portuguese: antidetonante Noun antiknock (plural antiknocks) Such a substance, usually tetraethyl lead (also MMT, MTBE and ethanol). Derived terms anti-knock index Translations substance to reduce the occurrence of engine knock Bulgarian: противодетонационен (protivodetonacionen) Polish: antydetonator m Portuguese: antidetonante m Wikiwand - on Seamless Wikipedia browsing. On steroids.