'Grandnephew' definitions:

Definition of 'grandnephew'

(from WordNet)
noun
A son of your niece or nephew [syn: great-nephew, grandnephew]

Definition of 'Grandnephew'

From: GCIDE
  • Grandnephew \Grand"neph"ew\, n. The grandson of one's brother or sister. [1913 Webster]