Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mullus, i, m., a kind of fish highly esteemed, the red mullet, barbel, Varr. R. R. 3, 17; Plin. 9, 17, 30, § 64: mulli barbati in piscinis, Cic. Att. 2, 1, 7; Juv. 5, 92; Sen. Ep. 95, 27 et saep.