Definition of cavalries:
(n) :
(military, usually historical, uncountable) The military arm of service that fights while riding horses.
(n) :
(military, countable) The branch of the military transported by fast light vehicles, also known as mechanized cavalry.
(n) :
(military, countable) An individual unit of this arm of service.
(n) :
(figurative) A source of rescue, especially in an emergency.