1. Several things formed together or considered as a whole: There was an aggregation of movie fans gathered outside the theatre hoping to catch a glimpse of their favorite stars.
2. A collection or a mass of distinct or varied things, people, etc.: The aggregates of stones under the water in the bed of the stream shimmered with many colors when the sun shined on it.
3. In biology, a number of organisms of the same, or different species, living closely together but less integrated than a society: In the tide pools by the ocean, the students from the local academy counted the various aggregates of different underwater sea creatures.