Source : Webster's Revised Unabridged Dictionary (1913)

Antivenin \An`ti*ve"nin\, n. [Written also {antivenen},
   {antivenine}.] [Pref. anti- + L. venenum poison.] (Physiol.
   Chem.)
   The serum of blood rendered antitoxic to a venom by repeated
   injections of small doses of the venom.