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