Source : Webster's Revised Unabridged Dictionary (1913)

Bestiality \Bes*tial"i*ty\, n. [F. bestialit['e].]
   1. The state or quality of being bestial.

   2. Unnatural connection with a beast.

Source : WordNet®

bestiality
     n : sexual activity between a person and an animal [syn: {zooerastia},
          {zooerasty}]