Related topics: Insects
1 [always + adverb/preposition]
if people swarm somewhere, they go there as a large, uncontrolled crowd:
Photographers were swarming around the princess.
if bees swarm, they leave a hive (=place where they live) in a large group to look for another home
swarm with somebody/somethingphrasal verb
The museum was swarming with tourists.