Entry 2 senses Webster, 1913

Synergistic

/sĭnˌ-ẽrj-ĭs'-tĭk/ · Syn·er·gis·tic · IPA /sˌɪnərdʒˈɪstɪk/

01 a. Of or pertaining to synergism.

1.
Of or pertaining to synergism.
2.
Cooperating; synergetic.