The Collaborative International Dictionary of English v.0.48:

Accumulate \Ac*cu"mu*late\, v. t. [imp. & p. p. Accumulated;
   p. pr. & vb. n. Accumulating.] [L. accumulatus, p. p. of
   accumulare; ad + cumulare to heap. See Cumulate.]
   To heap up in a mass; to pile up; to collect or bring
   together; to amass; as, to accumulate a sum of money.
   [1913 Webster]

   Syn: To collect; pile up; store; amass; gather; aggregate;
        heap together; hoard.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

accumulated \accumulated\ adj.
   1. 1 brought together into a group or crowd the accumulated
      letters in my office

   Syn: assembled, collected, congregate, massed
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

accumulated
    adj 1: periodically accumulated over time; "accrued interest";
           "accrued leave" [syn: accrued, accumulated]