From Longman Dictionary of Contemporary Englishpounderpound‧er /ˈpaʊndə $ -ər/ noun → a 3-pounder/24-pounder/185-pounder etc
Examples from the Corpus
pounder• To cap it off, the last but one trap contained a ten pounder.• Not simply on Tring Reservoirs or the home counties gravel pits do men now sit for a ten pounder anymore. 