The Collaborative International Dictionary of English v.0.48:

Intimidate \In*tim"i*date\, v. t. [imp. & p. p. Intimidated;
   p. pr. & vb. n. Intimidating.] [LL. intimidatus, p. p. of
   intimidare to frighten; pref. in- in + timidus fearful,
   timid: cf. F. intimider. See Timid.]
   To make timid or fearful; to inspire of affect with fear; to
   deter, as by threats; to dishearten; to abash.
   [1913 Webster]

         Now guilt, once harbored in the conscious breast,
         Intimidates the brave, degrades the great. --Johnson.

   Syn: To dishearten; dispirit; abash; deter; frighten;
        terrify; daunt; cow.
        [1913 Webster]

WordNet (r) 3.0 (2006):

intimidate
    v 1: make timid or fearful; "Her boss intimidates her"
    2: to compel or deter by or as if by threats [syn: intimidate,
       restrain]

Moby Thesaurus II by Grady Ward, 1.0:

115 Moby Thesaurus words for "intimidate":
   abash, admonish, alarm, awe, badger, bait, be imminent, beat down,
   blackjack, bludgeon, bluff, bluster, bluster and bluff,
   bluster out of, bounce, brag, break, browbeat, bulldoze, bully,
   bullyrag, castrate, caution, chivy, clamp down on, coerce,
   comminate, compel, constrain, cow, cry out against, daunt,
   demoralize, denounce, despotize, dismay, disquiet, dissuade,
   domineer, domineer over, dragoon, enslave, expostulate, force,
   forebode, frighten, frighten off, gasconade, grind, grind down,
   harass, hector, henpeck, hijack, hound, huff, keep down,
   keep under, kid out of, look threatening, lord it over, lower,
   menace, oblige, oppress, out-herod Herod, overawe, overbear,
   overmaster, override, petrify, press heavy on, rage, rant, rave,
   remonstrate, repress, ride, ride over, ride roughshod over,
   roister, rollick, ruffle, scare, shanghai, slang, splutter,
   sputter, steamroller, storm, strong-arm, subjugate, suppress,
   swagger, swashbuckle, systematically terrorize, talk out of,
   terrify, terrorize, threaten, trample down, trample upon,
   tread down, tread upon, tyrannize, tyrannize over, unman,
   unpersuade, use violence, utter threats against, vapor,
   walk all over, walk over, warn, weigh heavy on