The term often used interchangeably with art informel or Lyrical Abstraction and applied to the movement in abstract art that flourished in Europe, especially in France, in the late 1940s and 1950s. As early as 1899 Félix Fénéon referred to the work of the Impressionists as ‘tachiste’ to distinguish it from the more studied technique of the Derived from the French word signifying a blot, stain or mark, the term emphasizes the spontaneous gestural quality that characterizes much of this work.
Source: Tachisme — Google Arts & Culture