: 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
Jay Nordlinger, National Review, 3 Mar. 2025
By calculating the positions of nearby stellar clusters through time, the researchers identified two main suspects that could have housed the supernova progenitor.
—Michael Irving, New Atlas, 2 Mar. 2025
Mary Walrath-Holdridge, USA TODAY, 27 Feb. 2025
In these subsequent ages, green forests have clustered in the rocky canyons where the moisture was sure.
—Frank C. Hibben, Outdoor Life, 27 Feb. 2025
See All Example Sentences for cluster
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
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Noun
But a cluster of countries — a cluster of liberal democracies, confident in their values and armed to the teeth — could make a significant contribution.
—Jay Nordlinger, National Review, 3 Mar. 2025
By calculating the positions of nearby stellar clusters through time, the researchers identified two main suspects that could have housed the supernova progenitor.
—Michael Irving, New Atlas, 2 Mar. 2025
Verb
In areas like Gaines, where school districts and communities with high exemption rates are clustered together and contain a high concentration of the people most susceptible to infection, such as children under 18, the spread is more likely to occur.
—Mary Walrath-Holdridge, USA TODAY, 27 Feb. 2025
In these subsequent ages, green forests have clustered in the rocky canyons where the moisture was sure.
—Frank C. Hibben, Outdoor Life, 27 Feb. 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 13 Mar. 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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