Cluster

clus•ter /ˈklʌstɚ/n. [countable]a number of things of the same kind, growing or held together;

bunch:a cluster of flowers.a group of persons or things close together:That cluster of stars is held together by gravitation.

v. to form or gather in a cluster: [no object]The students clustered around the professor.[~ + object]The students were clustered around the professor.

WordReference Random House Learner's Dictionary of American English © 2015

From Middle English cluster, from Old English cluster, clyster (“cluster, bunch, branch”), from Proto-Germanic *klus-, *klas- (“to clump, lump together”) + Proto-Germanic *-þrą (instrumental suffix), related to Low German Kluuster (“cluster”), Dutch dialectal klister (“cluster”), Swedish kluster (“cluster”), Icelandic klasi (“cluster; bunch of grapes”).