| Noun | 1. | supremo - the most important person in an organization Britain, Great Britain, U.K., UK, United Kingdom, United Kingdom of Great Britain and Northern Ireland - a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom big cheese, big deal, big enchilada, big fish, big gun, big shot, big wheel, head honcho - an important influential person; "he thinks he's a big shot"; "she's a big deal in local politics"; "the Qaeda commander is a very big fish" |