grand·fa·ther / ˈgran(d)ˌfä[voicedth]ər/ • n. the father of one's father or mother. ∎ the person who founded or originated something: Freud is often called the grandfather of psychoanalysis. • v. [tr.] inf. exempt (someone or something) from a new law or regulation: smokers who worked here before the ban have been grandfathered. DERIVATIVES: grand·fa·ther·ly adj.