noun

a group of similar things or people positioned or occurring closely together.

clusters of creamy-white flowers

bunch,clump,collection,mass,knot,group,clutch,bundle,nest,agglomeration,conglomeration,aggregate,raceme,panicle,inflorescence,truss,crowd,huddle,gathering,throng,swarm,flock,pack,troupe,party,band,body,assemblage,congregation,gang,gaggle

verb

form a cluster or clusters.

the children clustered round her skirts

congregate,gather,collect,group,come together,assemble,huddle,crowd,flock,press,pack,mass,swarm