From Longman Dictionary of Contemporary Englishlight heavyweightˌlight ˈheavyweight noun [countable] DSOa boxer who weighs less than 79.38 kilograms, and who is heavier than a middleweight but lighter than a cruiserweight
Examples from the Corpus
light heavyweight• Last week in New York, he stopped respectable light heavyweight Merqui Sosa in only two rounds. 