grand-nephew [See grand a. 12 b.] The son of a nephew or niece. a1639Wotton Will in Walton Life (1651) c 9 My two Grand-nephews Albert Morton..and Thomas Bargrave.1826Miss Mitford VillageSer. ii. (1863) 346. 1860 Sala Baddington Peerage xxix, I'll have you out, were you twenty times my grand-nephew.