The term 'Pioneer of Installation Art' refers to the individual or individuals who are recognized as the founders or key figures in the development of installation art. Installation art is a form of art where the artist often transforms the space of the gallery or site itself into an integral part of the artwork. The term is often associated with artists such as Walter De Maria, Dan Flavin, and Yoko Ono, who began experimenting with this medium in the 1960s and 1970s. These artists broke away from traditional sculpture and painting to create immersive experiences that challenge the viewer's perception of space and time.