The Collaborative International Dictionary of English v.0.48:

Aggregation \Ag`gre*ga"tion\, n. [Cf. LL. aggregatio, F.
   agr['e]gation.]
   The act of aggregating, or the state of being aggregated;
   collection into a mass or sum; a collection of particulars;
   an aggregate.
   [1913 Webster]

         Each genus is made up by aggregation of species.
                                                  --Carpenter.
   [1913 Webster]

         A nation is not an idea only of local extent and
         individual momentary aggregation, but . . . of
         continuity, which extends in time as well as in
         numbers, and in space.                   --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

aggregation
    n 1: several things grouped together or considered as a whole
         [syn: collection, aggregation, accumulation,
         assemblage]
    2: the act of gathering something together [syn: collection,
       collecting, assembling, aggregation]

The Free On-line Dictionary of Computing (19 January 2023):

aggregation

    A composition technique for building a new
   object from one or more existing objects that support some
   or all of the new object's required interfaces.

   (1996-01-07)