vaccinia

(noun) a local infection induced in humans by inoculation with the virus causing cowpox in order to confer resistance to smallpox; normally lasts three weeks and leaves a pitted scar. Synonyms: vaccina, variola vaccine, variola vaccinia, variola vaccina.

(noun) a viral disease of cattle causing a mild skin disease affecting the udder; formerly used to inoculate humans against smallpox. Synonyms: cowpox.