The Collaborative International Dictionary of English v.0.48:

Dishearten \Dis*heart"en\ (d[i^]s*h[aum]rt"'n), v. t. [imp. & p.
   p. Disheartened (d[i^]s*h[aum]rt"'nd); p. pr. & vb. n.
   Disheartening.] [Pref. dis- + hearten.]
   To discourage; to deprive of courage and hope; to depress the
   spirits of; to deject.
   [1913 Webster]

         Regiments . . . utterly disorganized and disheartened.
                                                  --Macaulay.

   Syn: To dispirit; discourage; depress; deject; deter;
        terrify.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

disheartened \dis*heart"ened\ (d[i^]s*h[aum]rt"'nd), adj.
   made less hopeful or enthusiastic; as, their lack of interest
   disheartened the instructor. [Narrower terms: pessimistic
   (vs. optimistic)]

   Syn: demoralized, discouraged.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

disheartened
    adj 1: made less hopeful or enthusiastic; "desperate demoralized
           people looking for work"; "felt discouraged by the
           magnitude of the problem"; "the disheartened instructor
           tried vainly to arouse their interest" [syn:
           demoralized, demoralised, discouraged,
           disheartened]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "disheartened":
   bowed-down, cast down, dashed, dejected, depressed, despairing,
   despondent, desponding, discouraged, dispirited, down, downcast,
   downhearted, drooping, droopy, feeling low, heartless,
   hypochondriac, hypochondriacal, in low spirits, in the depths,
   in the doldrums, in the dumps, languishing, low, low-spirited,
   pessimistic, pining, spiritless, subdued, suicidal, weary of life,
   woebegone, world-weary