1. n. [Drilling]

A device fitted to the top joint of a casing string to hold a cement plug before it is pumped down the casing during the cementing operation. In most operations, a bottom plug is launched before the spacer or cement slurry. The top plug is released from the cement head after the spacer fluid. Most cement heads can hold both the top and bottom plugs. A manifold incorporated into the cement head assembly allows connection of a fluid circulation line.

See: cement head