The Collaborative International Dictionary of English v.0.48:

Wilt \Wilt\,
   2d pers. sing. of Will.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wilt \Wilt\, v. i. [imp. & p. p. Wilting.] [Written also welt,
   a modification of welk.]
   To begin to wither; to lose freshness and become flaccid, as
   a plant when exposed when exposed to drought, or to great
   heat in a dry day, or when separated from its root; to
   droop;. to wither. [Prov. Eng. & U. S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wilt \Wilt\, v. t.
   1. To cause to begin to wither; to make flaccid, as a green
      plant. [Prov. Eng. U. S.]
      [1913 Webster]

   2. Hence, to cause to languish; to depress or destroy the
      vigor and energy of. [Prov. Eng. & U. S.]
      [1913 Webster]

            Despots have wilted the human race into sloth and
            imbecility.                           --Dr. T.
                                                  Dwight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

wilt
    n 1: any plant disease characterized by drooping and shriveling;
         usually caused by parasites attacking the roots [syn:
         wilt, wilt disease]
    2: causing to become limp or drooping [syn: wilt, wilting]
    v 1: lose strength; "My opponent was wilting"
    2: become limp; "The flowers wilted" [syn: wilt, droop]

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "wilt":
   beat, blow, break, break down, burn out, cave in, collapse,
   come apart, come unstuck, conk out, crack up, crumble, debilitate,
   decline, desiccate, diminish, disintegrate, do in, do up, droop,
   drop, dry up, dwindle, enervate, exhaust, exude, fade, fade away,
   fag, fag out, fail, faint, fatigue, fizzle out, flag, frazzle,
   gasp, get tired, give out, give way, go downhill, go soft,
   go to pieces, grow weary, harass, hit the skids, jade, knock out,
   knock up, languish, lose strength, mummify, mummy, overfatigue,
   overstrain, overtire, overweary, pant, peak, peg out, perspire,
   peter out, pine, play out, poop, poop out, prostrate, puff,
   puff and blow, run down, run out, sag, sear, shrink, shrivel, sink,
   succumb, swag, sweat, swelter, tire, tire out, tire to death,
   tucker, use up, waste, waste away, weaken, wear, wear away,
   wear down, wear on, wear out, wear thin, weary, welter, wheeze,
   wind, wither, wither away, wizen, yield