The Collaborative International Dictionary of English v.0.48:

Hydrostatic \Hy`dro*stat"ic\, Hydrostatical \Hy`dro*stat"ic*al\,
   a. [Hydro-, 1 + Gr. ? causing to stand: cf. F. hydrostatique.
   See Static.]
   Of or relating to hydrostatics; pertaining to, or in
   accordance with, the principles of the equilibrium of fluids.
   [1913 Webster]

         The first discovery made in hydrostatics since the time
         of Archimedes is due to Stevinus.        --Hallam.
   [1913 Webster]

   Hydrostatic balance, a balance for weighing substances in
      water, for the purpose of ascertaining their specific
      gravities.

   Hydrostatic bed, a water bed.

   Hydrostatic bellows, an apparatus consisting of a
      water-tight bellowslike case with a long, upright tube,
      into which water may be poured to illustrate the
      hydrostatic paradox.

   Hydrostatic paradox, the proposition in hydrostatics that
      any quantity of water, however small, may be made to
      counterbalance any weight, however great; or the law of
      the equality of pressure of fluids in all directions.

   Hydrostatic press, a machine in which great force, with
      slow motion, is communicated to a large plunger by means
      of water forced into the cylinder in which it moves, by a
      forcing pump of small diameter, to which the power is
      applied, the principle involved being the same as in the
      hydrostatic bellows. Also called hydraulic press, and
      Bramah press. In the illustration, a is a pump with a
      small plunger b, which forces the water into the cylinder
      c, thus driving upward the large plunder d, which performs
      the reduced work, such as compressing cotton bales, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hydrostatic
    adj 1: relating to fluids at rest or to the pressures they exert
           or transmit; "hydrostatic pressure" [ant: hydrokinetic]