Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† thunnus (thynnus), i, m., = θύννος, the tunny or tunny-fish: Scomber thynnus, Linn.; Plin. 9, 15, 17, § 44 sq.; Hor. S. 2, 5, 44; Ov. Hal. 98; Mart. 10, 48, 12.