1. a collection of organisms in one location with no obvious social structure or social organization, possessing only a minimum of shared purpose or interdependence. Examples include people in a shopping mall, commuters on a subway platform, or a group of butterflies around a puddle of water. Compare group.

2. in statistics, a process of combining and summarizing a set of scores into a smaller set of scores that capture an aspect of the original set. Compare disaggregation. —aggregate vb. —aggregative adj.