Fluid head
From The Glossary of Digital Photography
A type of head used on a tripod to hold a camera. Typically, a fluid head is used with video cameras because they operate smoothly and can produce jerk-free pans of the camera. A fluid head was first patented by Eric Miller in 1946. The moving parts in a fluid head are immersed in lubricating fluid to provide the smoother operation, and it was this characteristic that gave the tripod head its name.
