Real Dictionary

vestal virgin in American English
in ancient Rome, any of a small group of virgin priestesses of Vesta, who, sworn to remain chaste, tended the sacred fire in her temple
one of four, later six, virgins consecrated to Vesta and to the tending of the sacred fire on her altar

vestal virgin in British English
noun: (in ancient Rome) one of the four, later six, virgin priestesses whose lives were dedicated to Vesta and to maintaining the sacred fire in her temple