boyo UK /ˈbɔɪ.əʊ/US /ˈbɔɪ.oʊ/ noun2 •(Ireland) A boy or lad. •(offensive) A stereotypically Welsh form of address for a man, usually younger than the speaker.“Don't be daft, boyo. First chance I get, and I'm skipping!” — 1968 formsboyos