Great-grandfather (noun)

1. The father of one's grandparent.
2. An ancestor of a specified degree in the direct line of descent.

Origin:

From great + grandfather, first attested in the late 17th century.

Examples:

1. He told me stories about his great-grandfather who fought in the war.
2. His great-grandfather was a pioneer in the field of medicine.
3. She looked just like her great-grandfather in the old photograph.
4. He never met his great-grandfather, but he heard many stories about him.
5. His great-grandfather passed down the tradition of wood carving to him.