The Collaborative International Dictionary of English v.0.48:

Extinguish \Ex*tin"guish\ ([e^]ks*t[i^][ng]"gw[i^]sh), v. t.
   [imp. & p. p. Extinguished([e^]ks*t[i^][ng]"gw[i^]sht); p
   pr. & vb. n. Extinguishing.] [L. extinguere, exstinguere;
   ex out + stinguere to quench. See Distinguish, Finish.]
   1. To quench; to put out, as a light or fire; to stifle; to
      cause to die out; to put an end to; to destroy; as, to
      extinguish a flame, or life, or love, or hope, a pretense
      or a right.
      [1913 Webster]

            A light which the fierce winds have no power to
            extinguish.                           --Prescott.
      [1913 Webster]

            This extinguishes my right to the reversion.
                                                  --Blackstone.
      [1913 Webster]

   2. To obscure; to eclipse, as by superior splendor.
      [1913 Webster]

            Natural graces that extinguish art.   --Shak
      .
      [1913 Webster]

WordNet (r) 3.0 (2006):

extinguish
    v 1: put an end to; kill; "The Nazis snuffed out the life of
         many Jewish children" [syn: snuff out, extinguish]
    2: put out, as of fires, flames, or lights; "Too big to be
       extinguished at once, the forest fires at best could be
       contained"; "quench the flames"; "snuff out the candles"
       [syn: snuff out, blow out, extinguish, quench] [ant:
       ignite, light]
    3: extinguish by crushing; "stub out your cigar" [syn: stub
       out, crush out, extinguish, press out]
    4: terminate, end, or take out; "Let's eliminate the course on
       Akkadian hieroglyphics"; "Socialism extinguished these
       archaic customs"; "eliminate my debts" [syn: extinguish,
       eliminate, get rid of, do away with]
    5: kill in large numbers; "the plague wiped out an entire
       population" [syn: eliminate, annihilate, extinguish,
       eradicate, wipe out, decimate, carry off]

Moby Thesaurus II by Grady Ward, 1.0:

143 Moby Thesaurus words for "extinguish":
   KO, abate, abolish, abscind, adumbrate, amputate, annihilate,
   asphyxiate, ban, banish, bar, blot out, blow out, bob, bottle up,
   call off, cancel, censor, choke, choke off, clamp down on, clip,
   complete, cork, cork up, crack down on, crop, crush, cull, cut,
   cut away, cut off, cut out, damp, damp down, delete, destroy, dim,
   dispose of, do away with, dock, douse, drop the curtain, drown,
   eclipse, eliminate, end off, enucleate, eradicate, except, excise,
   exclude, expunge, exterminate, extirpate, fake out, finalize,
   finish, fold up, gag, get it over, get over with, get through with,
   give the quietus, hold down, isolate, jump on, kayo, keep down,
   keep under, kibosh, kill, knock off, knock out, lop, mutilate,
   muzzle, nip, nullify, obliterate, obscure, out, outdo, overshadow,
   pare, peel, perfect, pick out, polish off, pour water on, prune,
   put down, put out, put paid to, put to shame, quash, quell, quench,
   remove, repress, root out, rule out, scrag, set apart, set aside,
   shave, shear, shoot down, show up, shut down on, silence,
   sit down on, sit on, slack, smash, smother, snuff, snuff out,
   squash, squelch, stamp out, stanch, stifle, strangle, strike off,
   strip, strip off, stultify, subdue, suffocate, suppress, take off,
   take out, throttle, trample out, trample underfoot, truncate,
   turn off, turn out, uproot, wipe, wipe out, zap