The Collaborative International Dictionary of English v.0.48:

Stifle \Sti"fle\, v. t. [imp. & p. p. Stifled; p. pr. & vb. n.
   Stifling.] [Freq. of OE. stif stiff; cf. Icel. st[imac]fla
   to dam up.]
   1. To stop the breath of by crowding something into the
      windpipe, or introducing an irrespirable substance into
      the lungs; to choke; to suffocate; to cause the death of
      by such means; as, to stifle one with smoke or dust.
      [1913 Webster]

            Stifled with kisses, a sweet death he dies.
                                                  --Dryden.
      [1913 Webster]

            I took my leave, being half stifled with the
            closeness of the room.                --Swift.
      [1913 Webster]

   2. To stop; to extinguish; to deaden; to quench; as, to
      stifle the breath; to stifle a fire or flame.
      [1913 Webster]

            Bodies . . . stifle in themselves the rays which
            they do not reflect or transmit.      --Sir I.
                                                  Newton.
      [1913 Webster]

   3. To suppress the manifestation or report of; to smother; to
      conceal from public knowledge; as, to stifle a story; to
      stifle passion.
      [1913 Webster]

            I desire only to have things fairly represented as
            they really are; no evidence smothered or stifled.
                                                  --Waterland.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stifle \Sti"fle\, n. [From Stiff.] (Far.)
   The joint next above the hock, and near the flank, in the
   hind leg of the horse and allied animals; the joint
   corresponding to the knee in man; -- called also stifle
   joint. See Illust. under Horse.
   [1913 Webster]

   Stifle bone, a small bone at the stifle joint; the patella,
      or kneepan.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stifle \Sti"fle\, v. i.
   To die by reason of obstruction of the breath, or because
   some noxious substance prevents respiration.
   [1913 Webster]

         You shall stifle in your own report.     --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stifle
    n 1: joint between the femur and tibia in a quadruped;
         corresponds to the human knee [syn: stifle, knee]
    v 1: conceal or hide; "smother a yawn"; "muffle one's anger";
         "strangle a yawn" [syn: smother, stifle, strangle,
         muffle, repress]
    2: smother or suppress; "Stifle your curiosity" [syn: stifle,
       dampen] [ant: excite, stimulate]
    3: impair the respiration of or obstruct the air passage of;
       "The foul air was slowly suffocating the children" [syn:
       suffocate, stifle, asphyxiate, choke]
    4: be asphyxiated; die from lack of oxygen; "The child
       suffocated under the pillow" [syn: suffocate, stifle,
       asphyxiate]

Moby Thesaurus II by Grady Ward, 1.0:

190 Moby Thesaurus words for "stifle":
   abate, allay, alleviate, asphyxiate, assuage, attemper, bake,
   bank the fire, bar, barricade, be in heat, black out, blaze, block,
   block up, blockade, bloom, blow out, blunt, boil, bolt, bottle up,
   broil, burke, burn, censor, chasten, check, chock, choke,
   choke off, clamp down on, close, close off, close tight, close up,
   combust, constipate, constrain, constrict, control, cook, cork,
   cork up, cover up, crack down on, crowd, crush, curb, damp,
   damp down, dampen, de-emphasize, deaden, debar, demolish, destroy,
   diminish, dog, douse, downplay, drown, dull, dumbfound, extenuate,
   extinguish, flame, flame up, flare, flare up, flicker, flush, fry,
   gag, garrote, gasp, glow, hold back, hold down, hold in,
   hugger-mugger, hush, hush up, hush-hush, incandesce, inhibit, jam,
   jump on, keep back, keep down, keep under, keep within bounds,
   kill, lay, lenify, lessen, lighten, lock, mitigate, moderate,
   modulate, muffle, mute, muzzle, obstruct, obtund, occlude, out,
   pack, palliate, pant, parch, play down, pour water on, prevent,
   put down, put out, put to silence, quash, quell, quench, quiet,
   quieten, radiate heat, reduce, reduce the temperature, repress,
   restrain, roast, scald, scorch, seethe, shimmer with heat, shush,
   shut down on, shut off, shut out, shut tight, silence, simmer,
   sit down on, sit on, slack, slacken, slow down, smash, smolder,
   smother, snuff, snuff out, sober, sober down, soft-pedal, soften,
   spark, squash, squeeze, squeeze shut, squelch, stagnate, stamp out,
   stanch, steam, stew, still, stop, stop the breath, stop up,
   strangle, strangulate, strike dumb, stultify, subdue, sublimate,
   suffocate, suppress, sweat, swelter, tame, temper, throttle, toast,
   tone down, trammel, trample out, trample underfoot, tune down,
   underplay, weaken, withhold