geezer [L19th] An informal word for a ‘man’, geezer represents a dialect pronunciation of the earlier form guiser (related to *disguise) meaning ‘mummer, someone who dresses up’. In recent use it sometimes has a connotation of shady dealing. Originally it was often used of an elderly man, but now it has strong cockney connotations and is usually approving, especially as diamond geezer, in use since at least the 1990s.