Anti-form is a term associated with a group of artists working in the United States in the late 1960s who embraced chance and other organic processes in the creation of their minimal sculptures.
Related to post-minimalism, anti-form sculptors worked from the principle that form should be derived from the inherent qualities of the chosen material. This differed from the approach of earlier minimalist sculptors who imposed order on their materials and confined themselves to fixed geometrical shapes and structures.
An example of anti-form is Robert Morris’ 1967 sculpture Untitled in which hanging strips of industrial felt were allowed to tumble to the ground in an arbitrary fashion. In this way the artist had to relinquish control of the final appearance of the artwork.