Webster's English Dictionary

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vaccine

1. vac.cine \vak-'se-n, 'vak-.\ aj [L vaccinus of or from cows, fr. vacca 
   cow; akin to Skt vas'a] [NL vaccinus, fr. L] cow 1: of, relating to, or 
   derived from cows; esp : derived from cows  infected with cowpox or 
   inoculated with its virus {~ lymph} 2: of or relating to vaccinia or 
   vaccination {a ~ pustule} 
2. vaccine n 1: matter or a preparation containing the virus of cowpox in a 
   form used fo r vaccination 2: a preparation of killed microorganisms, 
   living attenuated organisms, or  living fully virulent organisms that is 
   administered to produce or artificially increase immunity to a particular 
   disease