caetra (better than cētra), ae, f. [prob. Spanish],
a short Spanish shield , Verg. A. 7, 732 Serv.; Liv. 21, 27, 5; 28, 5, 11; Plin. 11, 39, 93, § 227; Tac. Agr. 36; Suet. Calig. 19; Luc. 7, 232; Sil. 3, 278; 3, 348 al.— Prov.: quis rotundam facere cetram nequeat? Varr. ap. Non. p. 82, 18.