The
idea of a
person being born without the
mother ever having had
sexual intercourse.
It's most often used when talking about the Christian Jesus, who was claimed to have been a miracle when given to Mary, since she was a virgin. Supposedly a gift from God.
Oddly, many people are not aware that it was common at that time for people of importance to be said to have been a virgin birth. It was also said about Julius Caesar, for example.