Tur·nus n. Zool. A common, large, handsome, American swallowtail butterfly, now regarded as one of the forms of Papilio glaucus syn. Jasoniades glaucus. The wings are yellow, margined and barred with black, and with an orange-red spot near the posterior angle of the hind wings. Called also tiger swallowtail. See Illust. under Swallowtail.