Synonyms for Swarm:

n.

lead, come, escort, haul off, drive, bring, conduct, deliver, shepherd, walk. assemblage, array, busload, constellation, collection, club, circle, age group. community, gaggle, flight, brace. infest, chirp, infestation, crawl, beat, hover, flutter, alight, fly. apiary (noun)
hive.
group (noun)
drove, horde.
large, moving group (noun)
throng, horde, troop, mass, drove, shoal, multitude, crowd, school.
numerousness (noun)
plenty, abundance, ampleness, crowd, numerousness, multitudinous, bounteousness.
swarm (noun)
pour, pullulate, teem, horde, drove, stream.
throng (noun)
study at crowd, mass, dense crowd, multitude, hive, troop, school, colony, shoal.

v.

move forward as a group (verb)
crawl, pullulate, teem, abound, stream.
number (verb)
enumerate, number, throng, count, abound, tally.
overrun (verb)
infest.

Other synonyms:

colony. multitude. crawl. mass. apiary
hive.
teem
pullulate, teem.
Other relevant words:
flight, assemblage, drive, collection, horde, mass, walk, circle, hive, troop, teem, pullulate, array, stream, infest, drove, crawl, gaggle, multitude, infestation, shoal, school, colony, pour.

Usage examples for swarm

  1. That both the south and north swarm with men 'less scrupulous, ' every one knows. – The Anti-Slavery Examiner, Omnibus by American Anti-Slavery Society
  2. At the rate they're coming, they'll be up to the door in a quarter of an hour, and then they'll swarm straight in on us. – Jack Haydon's Quest by John Finnemore