The Collaborative International Dictionary of English v.0.48:

Quench \Quench\, v. t. [imp. & p. p. Quenched; p. pr. & vb. n.
   Quenching.] [OE. quenchen, AS. cwencan in [=a]cwencan, to
   extinguish utterly, causative of cwincan, [=a]cwincan, to
   decrease, disappear; cf. AS. cw[imac]nan, [=a]cw[imac]nan, to
   waste or dwindle away.]
   1. To extinguish; to overwhelm; to make an end of; -- said of
      flame and fire, of things burning, and figuratively of
      sensations and emotions; as, to quench flame; to quench a
      candle; to quench thirst, love, hate, etc.
      [1913 Webster]

            Ere our blood shall quench that fire. --Shak.
      [1913 Webster]

            The supposition of the lady's death
            Will quench the wonder of her infamy. --Shak.
      [1913 Webster]

   2. To cool suddenly, as heated steel, in tempering.
      [1913 Webster]

   Syn: To extinguish; still; stifle; allay; cool; check.
        [1913 Webster]

WordNet (r) 3.0 (2006):

quenching
    n 1: the act of extinguishing; causing to stop burning; "the
         extinction of the lights" [syn: extinction,
         extinguishing, quenching]