Source : Webster's Revised Unabridged Dictionary (1913)

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.

   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.

            The atheist power shall quail, and confess his
            fears. I. Taylor. Stouter hearts than a woman's have
            quailed in this terrible winter.      --Longfellow.

   Syn: to cower; flinch; shrink; quake; tremble; blench;
        succumb; yield.