vaccinia

vac·cin·ia

noun \vak-ˈsin-ē-ə\

Definition of VACCINIA

1

a : cowpox b : a reaction to smallpox vaccine prepared from live vaccinia virus that may involve a rash, fever, headache, and body pain

2

: a poxvirus of the genus Orthopoxvirus (species Vaccinia virus) that differs from but is closely related to the viruses causing smallpox and cowpox and that includes a strain of uncertain natural origin used in making vaccines against smallpox—called also vaccinia virus

—vac·cin·i·al \-ē-əl\ adjective