grandnephew

[gran-nef-yoo, -nev-yoo, grand-] /ˈgrænˌnɛf yu, -ˌnɛv yu, ˈgrænd-/
noun
1.
a son of one's nephew or niece.
Origin
1630-40; grand- + nephew
British Dictionary definitions for grandnephew

grandnephew

/ˈɡrænˌnɛvjuː; -ˌnɛfjuː; ˈɡrænd-/
noun
1.
another name for great-nephew

great-nephew

noun
1.
a son of one's nephew or niece; grandson of one's brother or sister