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:

Accumulate \Ac*cu"mu*late\ ([a^]k*k[=u]"m[-u]*l[=a]t), v. i.
   To grow or increase in quantity or number; to increase
   greatly.
   [1913 Webster]

         Ill fares the land, to hastening ills a prey,
         Where wealth accumulates, and men decay. --Goldsmith.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Accumulate \Ac*cu"mu*late\ (-l[asl]t), a. [L. accumulatus, p. p.
   of accumulare.]
   Collected; accumulated. --Bacon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

accumulate
    v 1: get or gather together; "I am accumulating evidence for the
         man's unfaithfulness to his wife"; "She is amassing a lot
         of data for her thesis"; "She rolled up a small fortune"
         [syn: roll up, collect, accumulate, pile up,
         amass, compile, hoard]
    2: collect or gather; "Journals are accumulating in my office";
       "The work keeps piling up" [syn: accumulate, cumulate,
       conglomerate, pile up, gather, amass]

Moby Thesaurus II by Grady Ward, 1.0:

168 Moby Thesaurus words for "accumulate":
   accouple, accrue, advance, agglomerate, agglutinate, aggregate,
   aggroup, amass, appreciate, articulate, assemble, associate,
   backlog, balloon, band, batch, bloat, bond, boom, bracket, breed,
   bridge, bridge over, bring together, broaden, bulk, bunch,
   bunch together, bunch up, cement, chain, clap together, clump,
   cluster, collect, colligate, collocate, combine, compare, compile,
   comprise, concatenate, conglobulate, conglomerate, conjoin,
   conjugate, connect, copulate, corral, couple, cover, crescendo,
   cull, cumulate, develop, dig up, draw together, dredge up,
   drive together, embrace, encompass, fund, gain, gain strength,
   garner, garner up, gather, gather in, gather into barns,
   gather together, get ahead, get in, get together, glean, glue,
   go up, group, grow, grub, grub up, heap, heap up, hide, hive,
   hoard, hoard up, hold, include, increase, intensify, join,
   juxtapose, keep, knot, lay away, lay by, lay down, lay in,
   lay together, lay up, league, link, lump together, make up, marry,
   marshal, mass, match, merge, mobilize, mount, multiply, muster,
   pair, partner, pick, pick up, piece together, pile, pile up, pluck,
   proliferate, put away, put together, put up, raise, rake up, rally,
   rise, roll into one, roll up, round up, run up, save, save up,
   scare up, scrape together, scrape up, secrete, shoot up, snowball,
   solder, span, splice, spread, squirrel, squirrel away,
   stick together, stock, stock up, stockpile, store, store up,
   strengthen, swell, take in, take up, tape, tie, treasure,
   treasure up, unify, unite, wax, weld, whip in, widen, yoke