A diva is a celebrated female singer; a woman of outstanding talent in the world of opera, and by extension in theatre, cinema and popular music. The meaning of diva is closely related to that of prima donna.
The word entered the English language in the late 19th century. It is derived from the Italian noun diva, a female deity. The basic sense of the term is goddess.
(My definition includes actors, playwrights, novelists and any form of artistic expression.)