round up

1. The act of collecting or gathering together scattered cattle by riding around them and driving them in. [Western U.S.]

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.]

Collect or gather in a body, as in We'll have to round up some more volunteers for the food drive, or The police rounded up all the suspects. This term comes from the West, where since the mid-1800s it has been used for collecting livestock by riding around the herd and driving the animals together. By about 1875 it was extended to other kinds of gathering together.

Definition: collect, gather
Antonyms: disperse, scatter

The verb has one meaning:

Meaning #1: seek out and bring together