The Collaborative International Dictionary of English v.0.48:

Relieve \Re*lieve"\ (r?-l?v"), v. t. [imp. & p. p. Relieved
   (-l?vd"); p. pr. & vb. n. Relieving.] [OE. releven, F.
   relever to raise again, discharge, relieve, fr. L. relevare
   to lift up, raise, make light, relieve; pref. re- re- +
   levare to raise, fr. levis light. See Levity, and cf.
   Relevant, Relief.]
   1. To lift up; to raise again, as one who has fallen; to
      cause to rise. [Obs.] --Piers Plowman.
      [1913 Webster]

   2. To cause to seem to rise; to put in relief; to give
      prominence or conspicuousness to; to set off by contrast.
      [1913 Webster]

            Her tall figure relieved against the blue sky;
            seemed almost of supernatural height. --Sir W.
                                                  Scott.
      [1913 Webster]

   3. To raise up something in; to introduce a contrast or
      variety into; to remove the monotony or sameness of.
      [1913 Webster]

            The poet must . . . sometimes relieve the subject
            with a moral reflection.              --Addison.
      [1913 Webster]

   4. To raise or remove, as anything which depresses, weighs
      down, or crushes; to render less burdensome or afflicting;
      to alleviate; to abate; to mitigate; to lessen; as, to
      relieve pain; to relieve the wants of the poor.
      [1913 Webster]

   5. To free, wholly or partly, from any burden, trial, evil,
      distress, or the like; to give ease, comfort, or
      consolation to; to give aid, help, or succor to; to
      support, strengthen, or deliver; as, to relieve a besieged
      town.
      [1913 Webster]

            Now lend assistance and relieve the poor. --Dryden.
      [1913 Webster]

   6. To release from a post, station, or duty; to put another
      in place of, or to take the place of, in the bearing of
      any burden, or discharge of any duty.
      [1913 Webster]

            Who hath relieved you?                --Shak.
      [1913 Webster]

   7. To ease of any imposition, burden, wrong, or oppression,
      by judicial or legislative interposition, as by the
      removal of a grievance, by indemnification for losses, or
      the like; to right.
      [1913 Webster]

   Syn: To alleviate; assuage; succor; assist; aid; help;
        support; substain; ease; mitigate; lighten; diminish;
        remove; free; remedy; redress; indemnify.
        [1913 Webster]

WordNet (r) 3.0 (2006):

relieve
    v 1: provide physical relief, as from pain; "This pill will
         relieve your headaches" [syn: relieve, alleviate,
         palliate, assuage]
    2: free someone temporarily from his or her obligations [syn:
       take over, relieve]
    3: grant relief or an exemption from a rule or requirement to;
       "She exempted me from the exam" [syn: exempt, relieve,
       free] [ant: apply, enforce, implement]
    4: lessen the intensity of or calm; "The news eased my
       conscience"; "still the fears" [syn: still, allay,
       relieve, ease]
    5: save from ruin, destruction, or harm [syn: salvage,
       salve, relieve, save]
    6: relieve oneself of troubling information [syn: unbosom,
       relieve]
    7: provide relief for; "remedy his illness" [syn: remedy,
       relieve]
    8: free from a burden, evil, or distress
    9: take by stealing; "The thief relieved me of $100"
    10: grant exemption or release to; "Please excuse me from this
        class" [syn: excuse, relieve, let off, exempt]
    11: alleviate or remove (pressure or stress) or make less
        oppressive; "relieve the pressure and the stress"; "lighten
        the burden of caring for her elderly parents" [syn:
        relieve, lighten]

Moby Thesaurus II by Grady Ward, 1.0:

196 Moby Thesaurus words for "relieve":
   abate, abet, abridge, absolve, act for, aid, allay, alleviate,
   alternate, anesthetize, appease, assist, assuage, assure, avail,
   bail out, be light, bear a hand, bear up, befriend, benefit,
   benumb, bereave, bleed, break up, change places with, cheer,
   comfort, condole with, console, cover, crowd out, curtail, cushion,
   cut off, cut out, deaden, deaden the pain, decrease, deliver,
   deprive, deprive of, differ, differentiate, diminish, disburden,
   discharge, disencumber, disentitle, dispense, displace, dissent,
   disunify, divaricate, diverge, diversify, divest, do a hitch,
   do a stint, do a tour, do good, do time, doctor, double for, drain,
   dull, ease, ease matters, ease one of, encourage, enlist, excuse,
   favor, fill in, fill in for, foment, free, ghost, ghostwrite,
   give a boost, give a hand, give a lift, give comfort, give help,
   give relief, have a go, have little weight, have tenure, hearten,
   help, hold office, keep a watch, kick the beam, knock off,
   knock over, lay, lend a hand, lend one aid, lessen, let, liberate,
   lift, lighten, lighten one of, loot, lull, make light,
   make lighter, milk, mine, mitigate, moderate, mollify, numb,
   off-load, pad, palliate, pinch-hit, plunder, poultice,
   pour balm into, pour oil on, proffer aid, protect, put at ease,
   qualify, quiet, raise, rally, ransack, re-up, reassure, reclaim,
   redeem, reduce, reduce weight, reenlist, release, remedy,
   render assistance, replace, represent, rescue, restore,
   resuscitate, revive, rid, rifle, rob, salve, save, serve time,
   set at ease, set up, sign up, slacken, slake, soften, solace,
   soothe, spare, spell, spell off, stand in for, stick up, stupe,
   sub, subdue, subrogate, substitute, substitute for, succeed,
   succor, supersede, supplant, supply, support, swap places with,
   sympathize with, take away from, take from, take in tow, take over,
   take turns, tap, temper, time off, unballast, unburden,
   understudy for, unlade, unload, variate, variegate, vary,
   weigh lightly