: 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
Rachel Monroe, New Yorker, 25 Oct. 2025
If conditions are right, the clusters swirl into a storm known as a tropical wave or tropical depression.
—Doyle Rice, USA Today, 25 Oct. 2025
Hanna Park, CNN Money, 27 Oct. 2025
Most of the storm’s rainstorms and strong winds are clustered to the right side.
—Alex Harris, Miami Herald, 24 Oct. 2025
See All Example Sentences for cluster
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Noun
Five clusters of uniformed girls press together, arms uplifted, each holding up another girl who balances on one leg.
—Rachel Monroe, New Yorker, 25 Oct. 2025
If conditions are right, the clusters swirl into a storm known as a tropical wave or tropical depression.
—Doyle Rice, USA Today, 25 Oct. 2025
Verb
Scans revealed the magnets had clustered into four chains in the lower-right side of his abdomen, pulling together different sections of his bowel with their magnetic force, the report said, noting some imagery was distorted by the magnets.
—Hanna Park, CNN Money, 27 Oct. 2025
Most of the storm’s rainstorms and strong winds are clustered to the right side.
—Alex Harris, Miami Herald, 24 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 31 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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