(noun)
a large mass of people or things that are assembled closely and often moving together;
e.g. A swarm of people rushed off the train as soon as the doors opened.
(noun)
a series of similar geological phenomena or features that are close to each other in time or space, especially a number of earthquakes of similar magnitude occurring near a volcano;
e.g. The region has been experiencing an earthquake swarm over the past few weeks.
(verb)
to assemble or move as a large group/crowd, to fill a space with such a large group or (for a space) to contain such a large group;
e.g. At the end of the school day, children swarm out of the school gates.
(verb)
to climb up something using one's hands and feet;
e.g. She was easily able to swarm up the tall tree.