Burrs, which are seeds with rough hulls that have projecting spikes or hooks, use the projections to "latch onto" passing animals or people. The seeds then "hitch a ride" on these passers by to...
I cannot think of a one word antonym (word with the opposite meaning) to "disperse". However, to disperse some "thing" means to distribute that thing widely. Thus, a group of people can "disperse"...