Refers to art in which the process of creating it becomes the subject matter, first applied to the practice in Action Painting and Tachisme in the 1940s and 1950s, and later to the work of a group of artists working in the late 1960s. The style is characterized by the introduction of time, change, and chance, often resulting in documentation about the artwork's creation.

Source: Art & architecture Thesaurus 

http://vocab.getty.edu/page/aat/300022209