: 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
Christian Thorsberg, Smithsonian Magazine, 11 July 2025
In 2019, the CDC identified 22 outbreaks with the largest in two separate clusters in New York — 412 in New York state and 702 in New York City.
—Preston Fore, Fortune, 10 July 2025
arkansasonline.com, 8 July 2025
Policymakers can start with exploring opportunities to cluster around existing capacity in critical industries.
—Damien Ma, Foreign Affairs, 1 July 2025
See All Example Sentences for cluster
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Noun
The team’s genetic analysis focused on the Hox cluster: a family of genes found widely across the animal kingdom that fundamentally control an organism’s physical development.
—Christian Thorsberg, Smithsonian Magazine, 11 July 2025
In 2019, the CDC identified 22 outbreaks with the largest in two separate clusters in New York — 412 in New York state and 702 in New York City.
—Preston Fore, Fortune, 10 July 2025
Verb
Even in states with high vaccination coverage, pockets of unvaccinated people tend to cluster together.
—arkansasonline.com, 8 July 2025
Policymakers can start with exploring opportunities to cluster around existing capacity in critical industries.
—Damien Ma, Foreign Affairs, 1 July 2025
See All Example Sentences for cluster
Cite this Entry
“Cluster.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cluster. Accessed 19 Jul. 2025.
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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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