What does "grandnephew" mean?

A grandson of one's sibling; a son of one's nephew or niece. (Brother's grandson: fraternal grandnephew. Sister's grandson: sororal grandnephew.)

What is a synonym for "grandnephew"?

Common synonyms include: aunt, blood brother, brethren, brother, bub, bud.

noun

noun ·3 syllables ·Rare ·Advanced level

Noun

1
A grandson of one's sibling; a son of one's nephew or niece. (Brother's grandson: fraternal grandnephew. Sister's grandson: sororal grandnephew.)
2
a son of your niece or nephew wordnet

From grand- + nephew.