grandfather
n. countablen. the father of your father or mother. You might also call this person 'grandpa' or 'grandad'.
n. the father of one's father or mother. In legal or technical contexts, it can also refer to an ancestor or a previous version of a system that remains supported.
My grandfather lives in a small house by the sea.
Every summer, the children visit their grandfather on his farm to help with the harvest.
The legal dispute over the estate required the heirs to prove their direct lineage back to their great-great grandfather through a series of verified birth certificates.
The noun is derived from Middle English grandfadre, graundfadir, graunfadir, grauntfader, and other forms, from graunt (“big, large; great, important”) + fā̆der (“male parent, father; remoter male ancestor”), probably modelled after Middle French grandpere, grant pere (“male parent; remoter male ancestor”) (whence French grand-père); the English word is analysable as grand- + father. Superseded earlier eldfather, elderfather. The verb is derived from the noun.
From grandfather clause: see grandfather (etymology 1) and clause.
Commonly used as a title before a surname in formal contexts, though 'Grandpa' is more frequent in direct address.