Source : Webster's Revised Unabridged Dictionary (1913)

Excitatory \Ex*cit"a*to*ry\, a. [Cf. F. excitatoire.]
   Tending to excite; containing excitement; excitative.

Source : WordNet®

excitatory
     adj : (of drugs e.g.) able to excite or stimulate [syn: {excitant},
            {excitative}]