English Noun research octane number (plural research octane numbers) An octane number, used by the American Society for Testing and Materials to estimate the antiknock characteristics of a fuel at low engine speeds. Synonym: (initialism) RON Hypernyms octane number octane rating Coordinate terms motor octane number (MON) anti-knock index (AKI) Derived terms RON (abbreviation)Wikiwand - on Seamless Wikipedia browsing. On steroids.