(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.