The Collaborative International Dictionary of English v.0.48:

Redeem \Re*deem"\ (r?*d?m"), v. t. [imp. & p. p. Redeemed.
   (-d?md"); p. pr. & vb. n. Redeeming.] [F. r['e]dimer, L.
   redimere; pref. red-, re- re- + emere, emptum, to buy,
   originally, to take, cf. OIr. em (in comp.), Lith. imti. Cf.
   Assume, Consume, Exempt, Premium, Prompt,
   Ransom.]
   1. To purchase back; to regain possession of by payment of a
      stipulated price; to repurchase.
      [1913 Webster]

            If a man sell a dwelling house in a walled city,
            then he may redeem it within a whole year after it
            is sold.                              --Lev. xxv.
                                                  29.
      [1913 Webster]

   2. Hence, specifically:
      (a) (Law) To recall, as an estate, or to regain, as
          mortgaged property, by paying what may be due by force
          of the mortgage.
      (b) (Com.) To regain by performing the obligation or
          condition stated; to discharge the obligation
          mentioned in, as a promissory note, bond, or other
          evidence of debt; as, to redeem bank notes with coin.
          [1913 Webster]

   3. To ransom, liberate, or rescue from captivity or bondage,
      or from any obligation or liability to suffer or to be
      forfeited, by paying a price or ransom; to ransom; to
      rescue; to recover; as, to redeem a captive, a pledge, and
      the like.
      [1913 Webster]

            Redeem Israel, O God, out of all his troubles. --Ps.
                                                  xxv. 22.
      [1913 Webster]

            The Almighty from the grave
            Hath me redeemed.                     --Sandys.
      [1913 Webster]

   4. (Theol.) Hence, to rescue and deliver from the bondage of
      sin and the penalties of God's violated law.
      [1913 Webster]

            Christ hath redeemed us from the curse of the law,
            being made a curse for us.            --Gal. iii.
                                                  13.
      [1913 Webster]

   5. To make good by performing fully; to fulfill; as, to
      redeem one's promises.
      [1913 Webster]

            I will redeem all this on Percy's head. --Shak.
      [1913 Webster]

   6. To pay the penalty of; to make amends for; to serve as an
      equivalent or offset for; to atone for; to compensate; as,
      to redeem an error.
      [1913 Webster]

            Which of ye will be mortal, to redeem
            Man's mortal crime?                   --Milton.
      [1913 Webster]

            It is a chance which does redeem all sorrows.
                                                  --Shak.
      [1913 Webster]

   To redeem the time, to make the best use of it.
      [1913 Webster]

WordNet (r) 3.0 (2006):

redeem
    v 1: save from sins [syn: deliver, redeem, save]
    2: restore the honor or worth of
    3: to turn in (vouchers or coupons) and receive something in
       exchange
    4: exchange or buy back for money; under threat [syn: ransom,
       redeem]
    5: pay off (loans or promissory notes) [syn: redeem, pay
       off]
    6: convert into cash; of commercial papers

Moby Thesaurus II by Grady Ward, 1.0:

174 Moby Thesaurus words for "redeem":
   abet, abide by, absolve, acknowledge, aid, amend, amortize, assist,
   atone, atone for, avail, bail out, balance, be faithful to,
   bear a hand, bear the expense, befriend, benefit, buy, buy back,
   carry out, cash in, change, change for, chip in, clear, comfort,
   commute, compensate, compensate for, compound for, convert,
   counterbalance, counterpoise, countervail, defray, defray expenses,
   deliver, discharge, disenthrall, do good, doctor, dub in, ease,
   emancipate, exchange, expiate, extract, extricate, favor, finance,
   foot the bill, free, fund, get back, give a boost, give a hand,
   give a lift, give help, give place to, give salvation,
   give satisfaction, go Dutch, help, honor, honor a bill, keep,
   keep faith with, lend a hand, lend one aid, liberate, lift,
   liquidate, live down, loose, make accounts square, make amends,
   make compensation, make do with, make good, make matters up,
   make reparation, make right, make up, make up for, make way for,
   manumit, new-model, offer in exchange, offset, outweigh, pay for,
   pay in full, pay off, pay the bill, pay the forfeit,
   pay the penalty, pay the piper, pay the shot, pay up, perform,
   proffer aid, propitiate, protect, put up with, rally, ransom,
   re-form, recapture, reclaim, recompense, recoup, recover,
   recuperate, recycle, redress, refashion, reform, regain,
   regenerate, rehabilitate, reinstate, release, relieve, remedy,
   remodel, render assistance, renew, renovate, reoccupy, repair,
   replevin, replevy, repossess, repurchase, rescue, reshape, restore,
   restore self-respect, resume, resuscitate, retake, retire,
   retrieve, revindicate, revive, ring in, salvage, satisfy, save,
   see through, set free, set off, set straight, set up, settle,
   shift with, square, square accounts, square it, square things,
   stand the costs, strike a balance, substitute, succor, switch,
   take back, take in exchange, take in tow, take up, trade in,
   unbind, unchain, win back