The Collaborative International Dictionary of English v.0.48:

Hydraulic \Hy*drau"lic\, a. [F. hydraulique, L. hydraulicus, fr.
   Gr. ?, ?, a water organ; "y`dwr water + ? flute, pipe. See
   Hydra.]
   Of or pertaining to hydraulics, or to fluids in motion;
   conveying, or acting by, water; as, an hydraulic clock,
   crane, or dock.
   [1913 Webster]

   Hydraulic accumulator, an accumulator for hydraulic
      machinery of any kind. See Accumulator, 2.

   Hydraulic brake, a cataract. See Cataract, 3.

   Hydraulic cement, a cement or mortar made of hydraulic
      lime, which will harden under water.

   Hydraulic elevator, a lift operated by the weight or
      pressure of water.

   Hydraulic jack. See under Jack.

   Hydraulic lime, quicklime obtained from hydraulic
      limestone, and used for cementing under water, etc.

   Hydraulic limestone, a limestone which contains some clay,
      and which yields a quicklime that will set, or form a
      firm, strong mass, under water.

   Hydraulic main (Gas Works), a horizontal pipe containing
      water at the bottom into which the ends of the pipes from
      the retorts dip, for passing the gas through water in
      order to remove ammonia.

   Hydraulic mining, a system of mining in which the force of
      a jet of water is used to wash down a bank of gold-bearing
      gravel or earth. [Pacific Coast]

   Hydraulic press, a hydrostatic press. See under
      Hydrostatic.

   Hydraulic propeller, a device for propelling ships by means
      of a stream of water ejected under water rearward from the
      ship.

   Hydraulic ram, a machine for raising water by means of the
      energy of the moving water of which a portion is to be
      raised. When the rush of water through the main pipe d
      shuts the valve at a, the momentum of the current thus
      suddenly checked forces part of it into the air chamber b,
      and up the pipe c, its return being prevented by a valve
      at the entrance to the air chamber, while the dropping of
      the valve a by its own weight allows another rush through
      the main pipe, and so on alternately.

   Hydraulic valve. (Mach.)
   (a) A valve for regulating the distribution of water in the
       cylinders of hydraulic elevators, cranes, etc.
   (b) (Gas Works) An inverted cup with a partition dipping into
       water, for opening or closing communication between two
       gas mains, the open ends of which protrude about the
       water.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cement \Ce*ment"\ (s[e^]*m[e^]nt" or s[e^]m"[e^]nt), n. [OF.
   cement, ciment, F. ciment, fr. L. caementum a rough, unhewn
   stone, pieces or chips of marble, from which mortar was made,
   contr. fr. caedimentum, fr. caedere to cut, prob. akin to
   scindere to cleave, and to E. shed, v. t.]
   1. Any substance used for making bodies adhere to each other,
      as mortar, glue, etc.
      [1913 Webster]

   2. A kind of calcined limestone, or a calcined mixture of
      clay and lime, for making mortar which will harden under
      water.
      [1913 Webster]

   3. The powder used in cementation. See Cementation, n., 2.
      [1913 Webster]

   4. Bond of union; that which unites firmly, as persons in
      friendship, or men in society. "The cement of our love."
      [1913 Webster]

   5. (Anat.) The layer of bone investing the root and neck of a
      tooth; -- called also cementum.
      [1913 Webster]

   Hydraulic cement. See under Hydraulic.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hydraulic cement
    n 1: a cement that hardens under water; made by heating
         limestone and clay in a kiln and pulverizing the result
         [syn: hydraulic cement, Portland cement]