Patois is a spoken form of a language used by people in a small area, different from the national or standard language. That is the dictionary picture: local talk, not the schoolbook kind. The word is borrowed from French and in English it still feels a little specialist — linguists, travel writing, novels. Handle it with care. Older speakers sometimes used it as if the local way of talking were 'not real language', only a rough leftover. That looking-down tone is part of the word's history, even when a writer does not mean to sneer. Though actually, what people call patois is often a full, rule-governed way of speaking. In the Caribbean, Patois (especially Jamaican Patois) is the everyday name for a creole language, not 'broken English'. So the tidy definition ('a small-area dialect') is tidier than the world: sometimes it means a village dialect, and sometimes it is the name of a language with millions of speakers.