From Middle English swarm, from Old English swearm, from Proto-West Germanic *swarm, from Proto-Germanic *swarmaz, from Proto-Indo-European *swer-.

The verb is from Middle English swarmen, swermen, from Old English swierman, from Proto-West Germanic *swarmijan, from Proto-Germanic *swarmijaną, from the noun.

• (America) IPA: /swɔɹm/
• (RP) IPA: /swɔːm/

swarm (plural swarms)

1. A large number of insects, especially when in motion or (for bees) migrating to a new colony.
   • 1671, John Milton, “Samson Agonistes, […].”, in Paradise Regain'd. A Poem. In IV Books. To which is Added, Samson Agonistes, London: […] J[ohn] M[acock] for John Starkey […], →OCLC ↗, page 10 ↗, lines 19–21:

     […] reſtleſs thoughts, that like a deadly ſwarm / Of Hornets arm'd […] ruſh upon me thronging,

2. A mass of people, animals or things in motion or turmoil.

   a swarm of meteorites

   • 1705, J[oseph] Addison, Remarks on Several Parts of Italy, &c. in the Years 1701, 1702, 1703, London: […] Jacob Tonson, […], →OCLC ↗:

     those prodigious swarms that had settled themselves in every part of it [Italy]

3. (computing) A group of nodes sharing the same torrent in a BitTorrent network.
4. (seismology) A number of small earthquakes (or other seismic events) occurring, with no clear cause, in a specific area within a relatively short space of time.

• French: essaim (flying insects), grouillement (crawling insects)
• German: Schwarm
• Italian: sciame, nugolo
• Portuguese: enxame, nuvem (in flight), correição (especially ants)
• Russian: рой
• Spanish: enjambre, nube

• French: nuée, essaim
• German: Schwarm
• Portuguese: multidão, enxame, turba, turbamulta, turbilhão, tropel, roda-viva, barafunda
• Russian: (people) толпа́
• Spanish: multitud, muchedumbre, masa, aglomeración, barahúnda

swarm (swarms, present participle swarming; simple past and past participle swarmed)

1. (intransitive) To move as a swarm.
   • 1915, G[eorge] A. Birmingham [pseudonym; James Owen Hannay], chapter I, in Gossamer, New York, N.Y.: George H. Doran Company, →OCLC ↗:

     There is an hour or two, after the passengers have embarked, which is disquieting and fussy. Mail bags, so I understand, are being put on board. Stewards, carrying cabin trunks, swarm in the corridors.

2. (intransitive) To teem, or be overrun with insects, people, etc.
   • 1596 (date written; published 1633), Edmund Spenser, A Vewe of the Present State of Irelande […], Dublin: […] Societie of Stationers, […], →OCLC ↗; republished as A View of the State of Ireland […] (Ancient Irish Histories), Dublin: […] Society of Stationers, […] Hibernia Press, […] [b]y John Morrison, 1809, →OCLC ↗:

     Every place swarming with soldiers.

3. (transitive) To fill a place as a swarm.
4. (transitive) To overwhelm as by an opposing army.
5. To climb by gripping with arms and legs alternately.
   • 1784, William Coxe, Travels into Poland, Russia, Sweden and Denmark:

     At the top was placed a piece of money, as a prize for those who could swarm up and seize it.

   • 1919, W[illiam] Somerset Maugham, “chapter 55”, in The Moon and Sixpence, [New York, N.Y.]: Grosset & Dunlap Publishers […], →OCLC ↗:

     She called out, and a boy came running along. He swarmed up a tree, and presently threw down a ripe nut. Ata pierced a hole in it, and the doctor took a long, refreshing draught.

6. To breed multitudes.
   • 1667, John Milton, “Book IX”, in Paradise Lost. […], London: […] [Samuel Simmons], and are to be sold by Peter Parker […]; [a]nd by Robert Boulter […]; [a]nd Matthias Walker, […], →OCLC ↗; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873, →OCLC ↗, lines 526–527:

     Not ſo thick ſwarm'd once the Soil / Bedropt with blood of Gorgon,

• French: essaimer (bees only)
• Italian: pullulare, sciamare
• Portuguese: enxamear
• Russian: кишеть
• Spanish: enjambrar

• Italian: pullulare
• Portuguese: fervilhar, pulular
• Russian: кише́ть
• Spanish: hormiguear, pulular

• Portuguese: infestar
• Russian: кишеть
• Spanish: atestar, infestar

• Russian: кара́бкаться