bucko UK /ˈbʌkəʊ/US /ˈbʌkoʊ/ noun2 •[before a noun] (informal) A boastful or bullying man. •(informal) Used as a term of address: young lad, friend, pal.He did an imitation of a pirate: "Arr, Arr, Arr, me buckos." — 2007 formsbuckoes · buckos