The Collaborative International Dictionary of English v.0.48:

Cumulation \Cu`mu*la"tion\ (k?`m?-l?"sh?n), n. [Cf. F.
   cumulation.]
   The act of heaping together; a heap. See Accumulation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cumulation
    n 1: a collection of objects laid on top of each other [syn:
         pile, heap, mound, agglomerate, cumulation,
         cumulus]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "cumulation":
   abundance, accumulation, acervation, agglomerate, agglomeration,
   aggregate, aggregation, amassment, assembling, backlog,
   bringing together, budget, chunk, collection, colluvies,
   commissariat, commissary, congeries, conglobation, conglomerate,
   conglomeration, cornucopia, dump, gathering, gleaning, glomeration,
   gob, heap, hoard, hunk, inventory, larder, lump, mass, material,
   materials, materiel, munitions, pile, plenitude, plenty,
   provisionment, provisions, rations, repertoire, repertory, rick,
   snowball, stack, stock, stock-in-trade, stockpile, store, stores,
   supplies, supply on hand, treasure, treasury, trove, wad