What is Privy?

Legal Definition
A person who is in privity with another. See Privies; Privity. As an adjective, the word has practically the same meaning as "private."
-- Black's Law Dictionary
Legal Definition
A privity in estate; a property right acquired from a lessee by contract or inheritance. See 119 N. C. 450, 56 Am. St. Rep. 678, 26 S. E. 33. One bearing a relationship of privity toward another. See 85 Iowa, 432, 52 N. W. 358.
-- Ballentine's Law Dictionary
Legal Definition
One who is a partaker, or has an interest in any action, matter or thing.
-- Bouviers Law Dictionary