- The definition of a grandniece is the female child of your niece or nephew.
An example of a grandniece is your brother’s granddaughter.
grandniece definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
the granddaughter of one's brother or sister; great-niece
grandniece definition by American Heritage Dictionary
A daughter of one's nephew or niece.