vac·cine (văk-sēn, văksēn′)
a. A preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a portion of the pathogen's structure, that is administered to prevent or treat infection by the pathogen and that functions by stimulating the production of an immune response.
b. A preparation from the cowpox virus that protects against smallpox when administered to an individual.
2. Computers A software program designed to detect and stop the progress of computer viruses.
[From Latin vaccīnus, of cows, from vacca, cow.]
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