cōs, cōtis, f. [Sanscr. ça, to whet, sharpen; cf. cautes],
I any hard stone, flintstone , Cic. Div. 1, 17, 33; Liv. 1, 36, 4 and 5; Curt. 4, 6, 8; 5, 3, 8; 8, 11, 23; Verg. E. 8, 43. —
II In partic., a whetstone, hone, grindstone , Plin. 36, 22, 47, § 164; Hor. C. 2, 8, 16; Quint. 2, 12, 8.—
B Trop.: ipsam iracundiam fortitudinis quasi cotem esse dicebant, Cic. Ac. 2 ( Luc. ), 44, 135; cf. id. Tusc. 4, 19, 43; Hor. A. P. 304.