: a number of similar things that occur together: such as
a
: two or more consecutive consonants or vowels in a segment of speech
b
: a group of buildings and especially houses built close together on a sizable tract in order to preserve open spaces larger than the individual yard for common recreation
c
: an aggregation of stars or galaxies that appear close together in the sky and are gravitationally associated
the Perseus cluster of galaxies
d
: a larger than expected number of cases of disease (such as leukemia) occurring in a particular locality, group of people, or period of time
e
: a number of computers networked together in order to function as a single computing system
Consisting of groups of inexpensive machines cobbled together, clusters in many ways have supplanted traditional supercomputers.—
Elizabeth K. Wilson
Elizabeth K. Wilson
clustered; clustering
ˈklə-st(ə-)riŋ 
1
: to collect into a cluster
cluster the tents together
2
: to furnish with clusters
The bridge was clustered with men and officers …—Herman Wouk
Herman Wouk
: to grow, assemble, or occur in a cluster
they clustered around the fire
Examples of cluster in a Sentence
Noun
a cluster of cottages along the shore
A small cluster of people had gathered at the scene of the accident.
Verb
The children clustered around the storyteller.
the mice clustered together into a small burrow
Recent Examples on the Web
Zoey Goto, Travel + Leisure, 2 June 2026
In some cases, flying with a cluster of booster engines might allow the rocket to continue its mission even if one of them fails.
—Stephen Clark, ArsTechnica, 2 June 2026
Ernesto Sagás, The Conversation, 26 May 2026
Barry Flanagan’s bronze hare, Roxy Paine’s Erratic, and Tony Smith’s Playground are clustered within easy distance of one another.
—David Hochman, Forbes.com, 26 May 2026
See All Example Sentences for cluster
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Noun
Shopping here is low-key but rewarding, with a cluster of indie stores that tap into the area’s free-spirited character.
—Zoey Goto, Travel + Leisure, 2 June 2026
In some cases, flying with a cluster of booster engines might allow the rocket to continue its mission even if one of them fails.
—Stephen Clark, ArsTechnica, 2 June 2026
Verb
Latinos are mostly clustered in and around Grand Junction, the largest metro hub between Denver and Salt Lake City.
—Ernesto Sagás, The Conversation, 26 May 2026
Barry Flanagan’s bronze hare, Roxy Paine’s Erratic, and Tony Smith’s Playground are clustered within easy distance of one another.
—David Hochman, Forbes.com, 26 May 2026
See All Example Sentences for cluster
Cite this Entry
“Cluster.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cluster. Accessed 3 Jun. 2026.
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Medical Definition
cluster
noun
clus·ter
ˈkləs-tər
: a larger than expected number of cases of disease (as leukemia) occurring in a particular locality, group of people, or period of time
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