The Collaborative International Dictionary
Post-impressionism \Post`-im*pres"sion*ism\, n. (Painting) In the broadest sense, the theory or practice of any of several groups of painters of the early 1900's, or of these groups taken collectively, whose work and theories have in common a tendency to reaction against the scientific and naturalistic character of impressionism and neo-impressionism. In a strict sense the term post-impressionism is used to denote the effort at self-expression, rather than representation, shown in the work of C['e]zanne, Matisse, etc.; but it is more broadly used to include cubism, the theory or practice of a movement in both painting and sculpture which lays stress upon volume as the important attribute of objects and attempts its expression by the use of geometrical figures or solids only; and futurism, a theory or practice which attempts to place the observer within the picture and to represent simultaneously a number of consecutive movements and impressions. In practice these theories and methods of the post-impressionists change with great rapidity and shade into one another, so that a picture may be both cubist and futurist in character. They tend to, and sometimes reach, a condition in which both representation and traditional decoration are entirely abolished and a work of art becomes a purely subjective expression in an arbitrary and personal language.
Douglas Harper's Etymology Dictionary
1910, from post- + impressionism.
Wiktionary
n. (alternative spelling of postimpressionism English)
Wikipedia
Post-Impressionism (also spelled Postimpressionism) is a predominantly French art movement that developed roughly between 1886 and 1905; from the last Impressionist exhibition to the birth of Fauvism. Post-Impressionism emerged as a reaction against Impressionists’ concern for the naturalistic depiction of light and colour. Due to its broad emphasis on abstract qualities or symbolic content, Post-Impressionism encompasses Neo-Impressionism, Symbolism, Cloisonnism, Pont-Aven School, and Synthetism, along with some later Impressionists' work. The movement was led by Paul Cézanne, Paul Gauguin, Vincent van Gogh, and Georges Seurat.
The term Post-Impressionism was first used by art critic Roger Fry in 1906. Critic Frank Rutter in a review of the Salon d'Automne published in Art News, 15 October 1910, described Othon Friesz as a "post-impressionist leader"; there was also an advert for the show The Post-Impressionists of France. Three weeks later, Roger Fry used the term again when he organized the 1910 exhibition, Manet and the Post-Impressionists, defining it as the development of French art since Manet.
Post-Impressionists extended Impressionism while rejecting its limitations: they continued using vivid colours, often thick application of paint, and real-life subject matter, but were more inclined to emphasize geometric forms, distort form for expressive effect, and use unnatural or arbitrary colour.