Definition of grande dames:
(n) :
A woman who is accomplished and influential, and is a respected senior figure in a particular field; a doyenne.
(n) :
A woman who is high-ranking, socially prominent, or has a dignified character, especially one who is advanced in age and haughty.
(n) :
(figurative) A very highly regarded and well-known institution or structure, or large conveyance such as a ship.