(1) A powder consisting of alumina, silica, lime, and other substances which hardens when mixed with water. Extensively used in the oil industry to bond casing to the walls of the wellbore.

(2) A secondary mineral growth of chemically precipitated material on the surfaces and in the interstices of clastic sediments. Authigenic clay minerals are not considered cement.

(3) To fix the casing firmly in the hole with cement, which is pumped through the drill pipe to the bottom of the casing and up into the annular space between the casing and the walls of the borehole. After the cement sets (hardens) it is drilled out of the casing. The casing can be perforated to allow reservoir fluids to enter the well.