Gathered or grouped closely together in a bunch or cluster.
From 'cluster' (Middle English from Old English 'clyster', from Germanic roots) + '-ed' (past participle suffix). The '-ed' form functions as an adjective.
The word 'cluster' comes from an old Germanic root meaning to stick or cling together. It's the same root that gives us 'crust' and 'accrue'—all about things sticking and building up together.
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