Troilus \Tro"i*lus\, n.; pl. L. {Troili}, E. {Troiluses}. [NL., fr. L. Troilus, Gr. ?, the son of Priam.] (Zool.) A large, handsome American butterfly ({Euph[oe]ades troilus}, or {Papilio troilus}). It is black, with yellow marginal spots on the front wings, and blue spots on the rear wings; -- also called {troilus butterfly}. [1913 Webster]