Lewis & Short

ter-gĕmĭnus, a, um, v. trigeminus.

trĭgĕmĭnus (collat. form, mostly poet., tergĕmĭnus), a, um, adj. [tresgeminus], three born at a birth: fratres, three twin-brothers.

  1. I. Lit., Liv. 1, 24, 1; cf.: tergeminos nasci certum est Horatiorum Curiatiorumque exemplo, Plin. 7, 3, 3, § 33: trigeminorum matres, Col. 3, 8, 1: trigemini filii, Plaut. Mil. 3, 1, 123.
    As subst.: trĭgĕmĭni, three brothers born at a birth, Liv. 1, 25, 1; Col. 2, 1, 3; 7, 6, 7; cf.: trigemino partu, id. 3, 10, 17: Horatius trigemina spolia prae se gerens, of the three twin-brothers, Liv. 1, 26, 2: Trigemini, the title of a comedy of Plautus, Gell. 7, 9, 7.
  2. II. Transf., in gen., threefold, triple, triform, = triplex (mostly poet.): trigeminae victoriae triplicem triumphum egistis, Liv. 6, 7, 4: tripectora tergemini vis Geryonai, Lucr. 5, 28; cf. of the same and of Cerberus: tergeminumque virum tergeminumque canem, Ov. Tr. 4, 7, 16; and of Cerberus: cui tres sunt linguae tergeminumque caput, Tib. 3, 4, 88: canis, Prop. 4 (5), 7, 52: tergemina Hecate (because she was also Luna and Diana; cf. triceps and triformis), Verg. A. 4, 511: tergemina dextra, i. e. of the three Graces, Stat. S. 3, 4, 83: jus tergeminae prolis. i. e. trium liberorum, id. ib. 4, 8, 21: pomorum tergemina natura, Plin. 15, 28, 34, § 114: verba illa Ciceronis in Pisonem (cap. 1) trigemina: decepit, fefellit, induxit, Gell. 13, 24, 22: certat tergeminis tollere honoribus, to the threefold honors, i. e. of the three highest magistracies, those of the curule ædile, the prætor, and the consul, Hor. C. 1, 1, 8: at tibi tergeminum mugiet ille sophos, thrice repeated, Mart. 3, 46, 8.
  3. III. Porta Trigemina, a gate, in the early times of Rome, at the foot of Mount Aventine, Liv. 4, 16, 2; 35, 10, 12; Plaut. Capt. 1, 1, 22; Plin. 18, 3, 4, § 15; Front. Aquaed. 5 al.; cf. Becker, Antiq. 1, p. 157 sq.