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]

Moby Thesaurus II by Grady Ward, 1.0:

120 Moby Thesaurus words for "aggregation":
   Anschluss, accumulation, acervation, addition, affiliation,
   agglomerate, agglomeration, agglutination, aggregate, agreement,
   alliance, amalgamation, amassment, articulation, assemblage,
   assembly, assimilation, association, backlog, blend, blending,
   bond, bracketing, cabal, cartel, centralization, chunk, clustering,
   coalescence, coalition, collection, colluvies, combination,
   combine, combo, communication, company, composition, concatenation,
   concourse, concurrence, confederacy, confederation, confluence,
   congeries, conglobation, conglomerate, conglomeration, conjugation,
   conjunction, connection, consolidation, conspiracy, convergence,
   copulation, coupling, crowd, cumulation, ecumenism, embodiment,
   encompassment, enosis, federalization, federation, fusion,
   gathering, glomeration, gob, group, hoard, hookup, hunk, inclusion,
   incorporation, integration, intercommunication, intercourse,
   interlinking, joinder, joining, jointure, junction, junta,
   knotting, league, liaison, linkage, linking, lump, marriage, mass,
   meeting, meld, melding, merger, merging, muster, package,
   package deal, pairing, reserve, ruck, snowball, solidification,
   splice, stockpile, symbiosis, syncretism, syndication, syneresis,
   synthesis, tie, tie-in, tie-up, trove, unification, union, wad,
   wedding, yoking



The Free On-line Dictionary of Computing (30 December 2018):

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)