Wiktionary:Word of the day/May 17

1. (historical)
   1. (medicine) Of, pertaining to, caused by, or characteristic of cowpox.
   2. (by extension, immunology) Of or pertaining to cowpox as a source of material for vaccination against smallpox; also, of or pertaining to such material used for vaccination.
2. (archaic) Of, pertaining to, or derived from cattle or cows.

vaccine n

1. (immunology)
   1. A substance given to stimulate a body's production of antibodies and provide immunity against a disease without causing the disease itself in the treatment, prepared from the agent that causes the disease (or a derivative of it; or a related, also effective, but safer disease), or a synthetic substitute; also, a dose of such a substance.
   2. The process of vaccination; immunization, inoculation.
   3. (historical) Material taken from cowpox pustules used for vaccination against smallpox.
   4. (also medicine, obsolete) The disease cowpox, especially as a source of material for vaccination against smallpox.
2. (figuratively)
   1. Something defensive or protective in nature, like a vaccine (sense 1.1).
   2. (computing) A software program which protects computers against, or detects and neutralizes, computer viruses and other types of malware; an antivirus.

vaccine v

1. (transitive, archaic) Synonym of vaccinate (“to treat (a person or an animal) with a vaccine to produce immunity against a disease”)

The British physician and scientist Edward Jenner, who pioneered the concept of vaccines and created the world’s first vaccine—the smallpox vaccine, was born on this day 275 years ago in 1749.