Gouache, opaque watercolour, or poster colour is paint consisting of pigment, water, a binding agents, usually dextrin or gum arabic. Gouache is designed to be used with opaque methods of painting and dries to a matte finish.
Gouache has been around for over 600 years. The term is derived from Italian guazzo, meaning water paint. It is similar to watercolour in that it can be rewetted, the two can easily be used together. It can be applied in opaque painting methods like acrylic or oil paints.