The term Outsider Art was originally used in 1972 by the critic Roger Cardinal as a direct English equivalent for art brut. This expression was invented by the painter Jean Dubuffet (1901-1985) in the late 1940s to describe the work produced by psychiatric patients and other visionaries and self-taught artists.

Art brut referred specifically to the idea of works in their "raw" state, "uncooked" by cultural and artistic influences (terms used by structural anthropologists such as LΘvi-Strauss). Raw also referred to the quality of these works as creation in its most direct and uninhibited form. Practitioners of art brut use a wide variety of styles and materials, bearing no relation to any activity in the world of fine art, and share only a compulsive need to create.

Outsider artists, by their very nature, tend not to be aware of each other, and do not form a cohesive group. The purest creators of art brut would not consider themselves artists at all, nor would it occur to them that they are producing art.

Outsider Art, used in a strict, academic sense, is a synonym for art brut. This is the sense in which it is used by Colin Rhodes, author of the standard text Outsider Art - Spontaneous Alternatives (Thames and Hudson, UK£7.99).

Confusingly, Outsider Art has also come to be used as an umbrella term, embracing a wide range of artistic practice. This use of the term Outsider Art is often commercially driven, used self-descriptively by the numerous commercial galleries that have sprung up around the world, dealing in a range of naive artists, visionaries and folk artists, as well as genuine Outsider Artists.

The magazine of Outsider Art, Raw Vision, published internationally, states: "The definition has become obscured by chronic misuse since its introduction in 1972. Outsider Arts should only apply to that rarity of art produced by those who do not know its name".