What does "morganatic" mean?

Morganatic: Pertaining to, in the manner of, or designating, a kind of marriage, called also left-handed marriage, between a man of superior rank and a woman of inferior, in which it is stipulated that neither the latter nor her children shall enjoy the rank or inherit the possessions of her husband. Brande & C. -- Mor`ga*nat"ic*al*ly, adv.