grandfather UK /ˈɡɹæn(d)ˌfɑːðə(r)/US /ˈɡɹæn(d)ˌfɑðɚ/noun 3verb 2forms 3 noun3 •a man whose child is one of your parents •A male forefather. •The archived older version of a file that immediately preceded the father file.File C is the grandfather because it was used to create file B. — 1983 verb2 •To be, or act as, a grandfather to. •(US) To retain discontinued laws or rules for (an object, individual or organization previously affected by them).Had the original work been permitted, it would be grandfathered into any code changes each time they occurred, Arvada officials said. The latest came in 2006. — 2009 formsgrandfathered · grandfathering · grandfathers