Source : Webster's Revised Unabridged Dictionary (1913)

Hydraulics \Hy*drau"lics\, n. [Cf. F. hydraulique.]
   That branch of science, or of engineering, which treats of
   fluids in motion, especially of water, its action in rivers
   and canals, the works and machinery for conducting or raising
   it, its use as a prime mover, and the like.

   Note: As a science, hydraulics includes hydrodynamics, or the
         principles of mechanics applicable to the motion of
         water; as a branch of engineering, it consists in the
         practical application of the mechanics of fluids to the
         control and management of water with reference to the
         wants of man, including canals, waterworks, hydraulic
         machines, pumps, water wheels, etc. Some writers treat
         hydraulics and hydrostatics as subdivisions of
         hydrodynamics.

Source : WordNet®

hydraulics
     n : study of the mechanics of fluids [syn: {fluid mechanics}]