Great-grandchild
Full definition of great-grandchild
Noun
great-grandchild
(plural great-grandchildren)- The son or daughter of one's grandchild.
Usage notes
Additional instances of "great-" can be prepended to the term, each indicating one further generation of descent. For large numbers of generations a number can be substituted, for example, "four-greats grandchild" or "four-times-great-grandchild".