Source : Webster's Revised Unabridged Dictionary (1913)

Instigate \In"sti*gate\, v. t. [imp. & p. p. {Instigated}; p.
   pr. & vb. n. {Instigating}.] [L. instigatus, p. p. of
   instigare to instigate; pref. in- in + a root akin to G.
   stechen to prick, E. stick. See {Stick}.]
   To goad or urge forward; to set on; to provoke; to incite; --
   used chiefly with reference to evil actions; as to instigate
   one to a crime.

         He hath only instigated his blackest agents to the very
         extent of their malignity.               --Bp.
                                                  Warburton.

   Syn: To stimulate; urge; spur; provoke; tempt; incite; impel;
        encourage; animate.

Source : WordNet®

instigate
     v 1: provoke or stir up; "incite a riot"; "set off great unrest
          among the people" [syn: {incite}, {set off}, {stir up}]
     2: serve as the inciting cause of; "She prompted me to call my
        relatives" [syn: {prompt}, {inspire}]