The Collaborative International Dictionary of English v.0.48:

Deplete \De*plete"\, v. t. [imp. & p. p. Depleted; p. pr. &
   vb. n. Depleting.] [From L. deplere to empty out; de- +
   plere to fill. Forined like replete, complete. See Fill,
   Full, a.]
   1. (Med.) To empty or unload, as the vessels of human system,
      by bloodletting or by medicine. --Copland.
      [1913 Webster]

   2. To reduce by destroying or consuming the vital powers of;
      to exhaust, as a country of its strength or resources, a
      treasury of money, etc. --Saturday Review.
      [1913 Webster]

WordNet (r) 3.0 (2006):

deplete
    v 1: use up (resources or materials); "this car consumes a lot
         of gas"; "We exhausted our savings"; "They run through 20
         bottles of wine a week" [syn: consume, eat up, use
         up, eat, deplete, exhaust, run through, wipe
         out]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "deplete":
   ablate, absorb, assimilate, bankrupt, bleed, bleed white, blow,
   blow out, burn up, clean out, clear, clear away, clear off,
   clear out, clear the decks, consume, cripple, debilitate, decrease,
   defecate, depreciate, dig into, digest, diminish, disable,
   dissipate, drain, drain of resources, draw, draw down, draw off,
   dribble away, dry up, eat, eat up, eliminate, empty, empty out,
   enfeeble, erode, evacuate, exhaust, expend, finish, finish off,
   gobble, gobble up, impoverish, ingest, lessen, milk, purge, reduce,
   remove, sap, scour out, shrink, spend, squander, suck dry, swallow,
   swallow up, sweep out, unclog, undermine, unfoul, use up, vent,
   void, wash up, waste, waste away, weaken, wear, wear away