Lewis & Short

sphinthrĭa or spintrĭa, ae, m. [from σφιγκτήρ, the contractile muscle of the anus], a male prostitute, Tac. A. 6, 1; Suet. Tib. 43; id. Calig. 16; id. Vit. 3 fin.; cf. Aus. Epigr. 119.