The Collaborative International Dictionary of English v.0.48:

Wither \With"er\, v. i. [imp. & p. p. Withered; p. pr. & vb.
   n. Withering.] [OE. wideren; probably the same word as
   wederen to weather (see Weather, v. & n.); or cf. G.
   verwittern to decay, to be weather-beaten, Lith. vysti to
   wither.]
   [1913 Webster]
   1. To fade; to lose freshness; to become sapless; to become
      sapless; to dry or shrivel up.
      [1913 Webster]

            Shall he hot pull up the roots thereof, and cut off
            the fruit thereof, that it wither?    --Ezek. xvii.
                                                  9.
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   2. To lose or want animal moisture; to waste; to pin? away,
      as animal bodies.
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            This is man, old, wrinkled, faded, withered. --Shak.
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            There was a man which had his hand withered. --Matt.
                                                  xii. 10.
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            Now warm in love, now with'ring in the grave.
                                                  --Dryden.
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   3. To lose vigor or power; to languish; to pass away. "Names
      that must not wither." --Byron.
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            States thrive or wither as moons wax and wane.
                                                  --Cowper.
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The Collaborative International Dictionary of English v.0.48:

Withering \With"er*ing\, a.
   Tending to wither; causing to shrink or fade. --
   With"er*ing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

withering
    adj 1: wreaking or capable of wreaking complete destruction;
           "possessing annihilative power"; "a devastating
           hurricane"; "the guns opened a withering fire" [syn:
           annihilative, annihilating, devastating,
           withering]
    2: making light of; "afire with annihilating invective"; "a
       devastating portrait of human folly"; "to compliments
       inflated I've a withering reply"- W.S.Gilbert [syn:
       annihilating, devastating, withering]
    n 1: any weakening or degeneration (especially through lack of
         use) [syn: atrophy, withering]