GRANDFATHER
grandfather, gramps, granddad, grandad, granddaddy, grandpa
(noun) the father of your father or mother
Source: WordNet® 3.1
Etymology 1
Noun
grandfather (plural grandfathers)
A father of someone's parent. [from 15th c.]
Synonym: Thesaurus:grandfather
Antonyms: grandmother (with regard to gender), grandchild, granddaughter, grandson (with regard to ancestry), Thesaurus:grandmother
(by extension) A male forefather.
Synonyms: highfather (rare), grandsire
Hypernyms
• grandparent
Hyponyms
• (father of someone's father): paternal grandfather
• (father of someone's mother): maternal grandfather
Verb
grandfather (third-person singular simple present grandfathers, present participle grandfathering, simple past and past participle grandfathered)
(transitive) To be, or act as, a grandfather to.
Etymology 2
Verb
grandfather (third-person singular simple present grandfathers, present participle grandfathering, simple past and past participle grandfathered)
(transitive, chiefly, US, law) To retain existing laws or rules for (a person or organization previously affected by them). [from 1950s]
(intransitive, chiefly, US, law) To retain existing laws or rules only for people or organizations previously affected by them, and to apply new laws or rules to the unaffected people or organizations. [from 1950s]
Source: Wiktionary
Grand"fa"ther, n.
Definition: A father's or mother's father; an ancestor in the next degree
above the father or mother in lineal ascent. Grandfather longlegs.
(Zoöl.) See Dady longlegs.
Source: Webster’s Unabridged Dictionary 1913 Edition