Meaning of double possessive

dou'ble posses'sive

Pronunciation: [key]
— Gram. Gram.
  1. a possessive construction consisting of a prepositional phrase with of containing a substantive in the possessive case, as of father's in He is a friend of father's. Also called
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.