The Collaborative International Dictionary of English v.0.48:

Attrition \At*tri"tion\, n. [L. attritio: cf. F. attrition.]
   1. The act of rubbing together; friction; the act of wearing
      by friction, or by rubbing substances together; abrasion.
      [1913 Webster]

            Effected by attrition of the inward stomach.
                                                  --Arbuthnot.
      [1913 Webster]

   2. The state of being worn. --Johnson.
      [1913 Webster]

   3. (Theol.) Grief for sin arising only from fear of
      punishment or feelings of shame. See Contrition.
      --Wallis.
      [1913 Webster]

WordNet (r) 3.0 (2006):

attrition
    n 1: erosion by friction [syn: abrasion, attrition,
         corrasion, detrition]
    2: the wearing down of rock particles by friction due to water
       or wind or ice [syn: grinding, abrasion, attrition,
       detrition]
    3: sorrow for sin arising from fear of damnation [syn:
       attrition, contrition, contriteness]
    4: a wearing down to weaken or destroy; "a war of attrition"
    5: the act of rubbing together; wearing something down by
       friction

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "attrition":
   abatement, ablation, abrasion, abrasive, absorption, apologies,
   assimilation, atomization, attenuation, ayenbite of inwit, beating,
   bitterness, blunting, brecciation, buffing, burning up, burnishing,
   chafe, chafing, comminution, consumption, contriteness, contrition,
   corrosion, crumbling, crushing, curtailment, cut, cutting, damping,
   deadening, debilitation, decrease, decrement, deliquescence,
   depletion, depreciation, derogation, detraction, detrition,
   devitalization, digestion, dilution, diminution, dip,
   disintegration, disparagement, dissipation, dissolution, drain,
   dressing, dulling, eating up, effemination, enervation,
   enfeeblement, erasure, erosion, evisceration, exhaustion,
   expending, expenditure, extenuation, extraction, fatigue, filing,
   finishing, fragmentation, fretting, galling, granulation,
   granulization, grating, grazing, grief, grinding, impairment,
   impoverishment, inanition, ingestion, languishment, lessening,
   levigation, limation, loss, mashing, mitigation, penance,
   penitently, polishing, pounding, powdering, rasping, reduction,
   regret, regretfulness, regrets, regretting, relaxation, remission,
   remorse, remorse of conscience, remorsefulness, repentance,
   repining, retraction, retrenchment, rubbing away, rue, ruth,
   sandblasting, sanding, scouring, scrape, scraping, scratch,
   scratching, scrub, scrubbing, scuff, shame, shamefacedness,
   shamefastness, shamefulness, shining, shortening, shredding,
   shrinkage, slackening, smashing, smoothing, softening, sorriness,
   sorrow, spending, squandering, thinning, trituration, truncation,
   using up, wastage, waste, wastefulness, wasting away, weakening,
   wear, wear and tear, wearing away, wearing down, wistfulness