The Collaborative International Dictionary of English v.0.48:

Stimulate \Stim"u*late\, v. t. [imp. & p. p. Stimulated; p.
   pr. & vb. n. Stimulating.] [L. stimulatus, p. p. of
   stimulare to prick or goad on, to incite, fr. stimulus a
   goad. See Stimulus.]
   1. To excite as if with a goad; to excite, rouse, or animate,
      to action or more vigorous exertion by some pungent motive
      or by persuasion; as, to stimulate one by the hope of
      reward, or by the prospect of glory.
      [1913 Webster]

            To excite and stimulate us thereunto. --Dr. J.
                                                  Scott.
      [1913 Webster]

   2. (Physiol.) To excite; to irritate; especially, to excite
      the activity of (a nerve or an irritable muscle), as by
      electricity.
      [1913 Webster]

   Syn: To animate; incite; encourage; impel; urge; instigate;
        irritate; exasperate; incense.
        [1913 Webster]

WordNet (r) 3.0 (2006):

stimulating
    adj 1: rousing or quickening activity or the senses; "a
           stimulating discussion" [ant: unexciting,
           unstimulating]
    2: that stimulates; "stimulant phenomena" [syn: stimulant,
       stimulating]
    3: making lively and cheerful; "the exhilarating effect of
       mountain air" [syn: exhilarating, stimulating]