the GNU version of the Collaborative International Dictionary of English
n. The granddaughter of one's brother or sister.
The Century Dictionary and Cyclopedia
n. A daughter of one's nephew or niece: correlative to granduncle and grandaunt.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a daughter of your niece or nephew
Word Usage
"Mrs. Nicoll was delighted with what she termed her grandniece's good sense, and gave her a handsome set of rubies, beside having her diamonds reset for her."