- Present participle of cluster.
- The action of the verb to cluster.
- A grouping of a number of similar things.
- (demographics) The grouping of a population based on ethnicity, economics or religion.
- (computing) The undesirable, contiguous grouping of elements in a hash table.
- (writing) A prewriting technique consisting of writing ideas down on a sheet of paper around a central idea within a circle, with the related ideas radially joined to the circle using rays.