The Collaborative International Dictionary of English v.0.48:

daunting \daunting\ adj.
   serving to discourage, dishearten, or intimidate;
   discouraging; disheartening. Opposite of encouraging.

   Syn: intimidating.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Daunt \Daunt\ (d[add]nt; 277), v. t. [imp. & p. p. Daunted; p.
   pr. & vb. n. Daunting.] [OF. danter, F. dompter to tame,
   subdue, fr. L. domitare, v. intens. of domare to tame. See
   Tame.]
   1. To overcome; to conquer. [Obs.]
      [1913 Webster]

   2. To repress or subdue the courage of; to check by fear of
      danger; to cow; to intimidate; to dishearten.
      [1913 Webster]

            Some presences daunt and discourage us. --Glanvill.

   Syn: To dismay; appall. See Dismay.
        [1913 Webster]

WordNet (r) 3.0 (2006):

daunting
    adj 1: discouraging through fear [syn: daunting,
           intimidating]