The Collaborative International Dictionary of English v.0.48:

Amass \A*mass"\, n. [OF. amasse, fr. ambusher.]
   A mass; a heap. [Obs.] --Sir H. Wotton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Amass \A*mass"\, v. t. [imp. & p. p. Amassed; p. pr. & vb. n.
   Amassing.] [F. ambusher, LL. amassare; L. ad + massa lump,
   mass. See Mass.]
   To collect into a mass or heap; to gather a great quantity
   of; to accumulate; as, to amass a treasure or a fortune; to
   amass words or phrases.
   [1913 Webster]

         The life of Homer has been written by amassing all the
         traditions and hints the writers could meet with.
                                                  --Pope.
   [1913 Webster]

   Syn: To accumulate; heap up; pile.
        [1913 Webster]

WordNet (r) 3.0 (2006):

amass
    v 1: collect or gather; "Journals are accumulating in my
         office"; "The work keeps piling up" [syn: accumulate,
         cumulate, conglomerate, pile up, gather, amass]
    2: 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]

Moby Thesaurus II by Grady Ward, 1.0:

129 Moby Thesaurus words for "amass":
   accouple, accumulate, agglomerate, agglutinate, aggregate, aggroup,
   articulate, assemble, associate, backlog, band, batch, bond,
   bracket, bridge, bridge over, bring together, 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, cull,
   cumulate, dig up, draw together, dredge up, drive together,
   embrace, encompass, garner, garner up, gather, gather in,
   gather into barns, gather together, get in, get together, glean,
   glue, group, grub, grub up, heap up, hide, hive, hoard, hoard up,
   hold, include, join, juxtapose, keep, knot, lay together, lay up,
   league, link, lump together, make up, marry, marshal, mass, match,
   merge, mobilize, muster, pair, partner, pick, pick up,
   piece together, pile up, pluck, put together, put up, raise,
   rake up, rally, roll into one, roll up, round up, save, save up,
   scare up, scrape together, scrape up, secrete, set aside, solder,
   span, splice, squirrel, squirrel away, stock up, stockpile,
   store up, take in, take up, tape, tie, treasure, treasure up,
   unify, unite, weld, whip in, yoke