Source : Webster's Revised Unabridged Dictionary (1913)

Vivisection \Viv`i*sec"tion\, n. [L. vivus alive + E. section:
   cf. F. vivisection. See {Vivid}, and {Section}.]
   The dissection of an animal while alive, for the purpose of
   making physiological investigations.

Source : WordNet®

vivisection
     n : the act of operating on living animals (especially in
         scientific research)