The Collaborative International Dictionary of English v.0.48:

Quail \Quail\, v. i. [imp. & p. p. Qualled; p. pr. & vb. n.
   Qualling.] [AS. cwelan to die, perish; akin to cwalu
   violent death, D. kwaal pain, G. qual torment, OHG. quelan to
   suffer torment, Lith. gelti to hurt, gela pain. Cf. Quell.]
   1. To die; to perish; hence, to wither; to fade. [Obs.]
      --Spenser.
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   2. To become quelled; to become cast down; to sink under
      trial or apprehension of danger; to lose the spirit and
      power of resistance; to lose heart; to give way; to
      shrink; to cower.
      [1913 Webster]

            The atheist power shall quail, and confess his
            fears. I. Taylor.
            Stouter hearts than a woman's have quailed in this
            terrible winter.                      --Longfellow.
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   Syn: to cower; flinch; shrink; quake; tremble; blench;
        succumb; yield.
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