Sort of a dance in the late 1960s and early 1970s. It is when a person, man or woman, goes on the dance floor, usually lays down but not always. Once in "position", they go freaking nuts and move around a lot, often flailing legs and arms in all directions. It often requires being very drunk to do it well.
One of my fraternity brothers was the absolute best at "gattoring”. He went total bonkers!