Round-up \Round"-up`\, n. The act of collecting or gathering together scattered cattle by riding around them and driving them in. [Western U.S.] Round-up \Round"-up`\, n. 1. A rounding up, or upward curvature or convexity, as in the deck of a vessel. 2. A gathering in of scattered persons or things; as, s round-up of criminals. [Colloq., U. S.]