The Collaborative International Dictionary of English v.0.48:

Appall \Ap*pall"\, n.
   Terror; dismay. [Poet.] --Cowper.
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The Collaborative International Dictionary of English v.0.48:

Appall \Ap*pall"\, v. t. [imp. & p. p. Appalled; p. pr. & vb.
   n. Appalling.] [OF. appalir to grow pale, make pale; a (L.
   ad) + p[^a]lir to grow pale, to make pale, p[^a]le pale. See
   Pale, a., and cf. Pall.]
   1. To make pale; to blanch. [Obs.]
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            The answer that ye made to me, my dear, . . .
            Hath so appalled my countenance.      --Wyatt.
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   2. To weaken; to enfeeble; to reduce; as, an old appalled
      wight. [Obs.] --Chaucer.
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            Wine, of its own nature, will not congeal and
            freeze, only it will lose the strength, and become
            appalled in extremity of cold.        --Holland.
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   3. To depress or discourage with fear; to impress with fear
      in such a manner that the mind shrinks, or loses its
      firmness; to overcome with sudden terror or horror; to
      dismay; as, the sight appalled the stoutest heart.
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            The house of peers was somewhat appalled at this
            alarum.                               --Clarendon.
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   Syn: To dismay; terrify; daunt; frighten; affright; scare;
        depress. See Dismay.
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The Collaborative International Dictionary of English v.0.48:

Appall \Ap*pall"\, v. i.
   1. To grow faint; to become weak; to become dismayed or
      discouraged. [Obs.] --Gower.
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   2. To lose flavor or become stale. [Obs.]
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Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "appall":
   abash, astound, awe, confound, daunt, discomfit, disconcert,
   disgust, dismay, faze, freeze, give offense, gross out, horrify,
   nauseate, offend, overawe, paralyze, petrify, put off, put out,
   repel, revolt, scare stiff, scare to death, shake, shock, sicken,
   strike dumb, strike terror into, stun, stupefy, take aback,
   terrify, turn the stomach