The Collaborative International Dictionary of English v.0.48:

Embolden \Em*bold"en\, v. t. [imp. & p. p. Emboldened; p. pr.
   & vb. n. Emboldening.]
   To give boldness or courage to; to encourage. --Shak.
   [1913 Webster]

         The self-conceit which emboldened him to undertake this
         dangerous office.                        --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

embolden
    v 1: give encouragement to [syn: cheer, hearten, recreate,
         embolden] [ant: dishearten, put off]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "embolden":
   abet, advocate, aid and abet, animate, assure, bolster, brace up,
   buck up, chance, cheer, chirk up, comfort, countenance, encourage,
   endorse, favor, go for, hazard, hearten, impel, inspire, inspirit,
   keep in countenance, nerve, reassure, shine upon, smile upon,
   steel, strengthen, subscribe, support, venture