Source : Webster's Revised Unabridged Dictionary (1913)

Veneficial \Ven`e*fi"cial\, Veneficious \Ven`e*fi"cious\, a.
   Acting by poison; used in poisoning or in sorcery. [Obs.]
   ``An old veneficious practice.'' --Sir T. Browne. --
   {Ven`e*fi"cious*ly}, adv. [Obs.]