The Collaborative International Dictionary of English v.0.48:

Round-up \Round"-up`\, n.
   1. The act of collecting or gathering together scattered
      cattle by riding around them and driving them in. [Western
      U.S.]
      [1913 Webster]

   2. A rounding up, or upward curvature or convexity, as in the
      deck of a vessel.
      [Webster 1913 Suppl.]

   2. A gathering in of scattered persons or things; as, a
      round-up of criminals. [Colloq., U. S.]
      [Webster 1913 Suppl.]