: 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
Mary Marlowe Leverette, Southern Living, 5 Oct. 2025
The number of localities passing moratoriums began rising in 2023 and 2024, mirroring trends in battery storage deployment, with a notable cluster in New York, according to a presentation last year by the Pacific Northwest National Laboratory.
—Jessica Coacci, Fortune, 4 Oct. 2025
Rick Burton, Sportico.com, 6 Oct. 2025
According to a Pew Research Center survey from earlier this year, regular users of CBS News placed themselves just left of center, clustered with other outlets like ABC News and Univision.
—Ted Johnson, Deadline, 6 Oct. 2025
See All Example Sentences for cluster
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Noun
The dark lavender-pink petals mature and fade to a soft pink, revealing a cluster of yellow stamens in the center.
—Mary Marlowe Leverette, Southern Living, 5 Oct. 2025
The number of localities passing moratoriums began rising in 2023 and 2024, mirroring trends in battery storage deployment, with a notable cluster in New York, according to a presentation last year by the Pacific Northwest National Laboratory.
—Jessica Coacci, Fortune, 4 Oct. 2025
Verb
Producers and directors naturally clustered in the middle, while those pushed to the ends were both physically and symbolically removed from the action.
—Rick Burton, Sportico.com, 6 Oct. 2025
According to a Pew Research Center survey from earlier this year, regular users of CBS News placed themselves just left of center, clustered with other outlets like ABC News and Univision.
—Ted Johnson, Deadline, 6 Oct. 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 9 Oct. 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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