a preparation of killed micro-organisms, e.g. viruses or bacteria, living inactivated organisms, or living fully infectious organisms, that is administered usu by injection to produce or artificially increase immunity to a particular disease
a preparation containing the virus of cowpox in a form used for vaccination
a piece of computer software designed to counteract electronic viruses
vaccinal /ʹvaksin(ə)l/ adj
[Latin vaccinus of or from cows, from vacca cow; from the use of vaccinia (cowpox) virus as the first vaccine]