clāva, ae, f. [root cel- of percello; cf. Gr. κλάω and clades].
I A knotty branch or stick , a staff , cudgel , club : adfer duas clavas... probas, Plaut. Rud. 3, 5, 20; Lucr. 5, 968: sternentes agmina clavā, Verg. A. 10, 318; Curt. 9, 4, 3; Ov. F. 1, 575; Cic. Verr. 2, 4, 43, § 94; Plin. 19, 1, 3, § 18; a bar , lever , Cato R. R. 13, 1.—As a weapon for exercising, used by young men, and esp. by soldiers, a foil , Cic. Sen. 16, 58; Veg. Mil. 1, 11.—As a badge of Hercules, Prop. 4 (5), 9, 39; Ov. H. 9, 117; id. M. 9, 114; 9, 236; * Suet. Ner. 53; cf. Paul. ex Fest. p. 62 Müll.—Hence, prov., clavam Herculi extorquere, for an impossible undertaking, Macr. S. 5, 3; Don. Vit. Verg.— Also Clava Herculis, a plant , otherwise called nymphea, Marc. Emp. 33.—
II In the lang. of economy, a graft , scion , Pall. Mart. 10, 12 and 13; cf. clavula.