Source : Webster's Revised Unabridged Dictionary (1913)

Vaccine \Vac"cine\, a. [L. vaccinus, fr. vacca a cow; cf. Skr.
   v[=a]c to bellow, to groan.]
   Of or pertaining to cows; pertaining to, derived from, or
   caused by, vaccinia; as, vaccine virus; the vaccine disease.
   -- n. The virus of vaccinia used in vaccination.

Source : WordNet®

vaccine
     n : immunogen consisting of a suspension of weakened or dead
         pathogenic cells injected in order to stimulate the
         production of antibodies [syn: {vaccinum}]