Allegra \a-lleg-ra, all(e)-gra\ as a girl's name is pronounced ah-LAY-grah. It is of Italian origin, and the meaning of Allegra is "gay and jaunty". The musical term "allegro" means "quickly, with a happy air". May have been originally coined as the name of Byron's illegitimate daughter in the 19th century. Ballerina Allegra Kent.