Source : Webster's Revised Unabridged Dictionary (1913)

Toxicology \Tox`i*col"o*gy\, n. [Gr. toxiko`n poison + -logy;
   cf. F. toxicologie. See {Toxic}. ]
   The science which treats of poisons, their effects,
   antidotes, and recognition; also, a discourse or treatise on
   the science.

Source : WordNet®

toxicology
     n : the branch of pharmacology that deals with the nature and
         effects and treatments of poisons