/ ˈklʌstə(r); NAmE / noun , verb
■ noun
1.
a group of things of the same type that grow or appear close together :
a cluster of stars
The plant bears its flowers in clusters.
a leukaemia cluster (= an area where there are more cases of the disease than you would expect)
2.
a group of people, animals or things close together :
a cluster of spectators
a little cluster of houses
3.
( phonetics ) a group of consonants which come together in a word or phrase, for example /str/ at the beginning of string :
a consonant cluster
■ verb
[ v + adv. / prep. ] cluster (together) to come together in a small group or groups :
The children clustered together in the corner of the room.
The doctors clustered anxiously around his bed.
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WORD ORIGIN
Old English clyster ; probably related to clot .