From Longman Dictionary of Contemporary Englishgrandaddygran‧dad‧dy, granddaddy /ˈɡrændædi/ noun (plural grandaddies) [countable] American English informal 1 SSFFAMILYgrandfather2 → the grandaddy of something
Examples from the Corpus
grandaddy• His grandaddy used to work for three dollars a day.• Plenty of booze and chow round out the celebration, considered the grandaddy of July Fourth blasts. 