Source : Webster's Revised Unabridged Dictionary (1913)

Piezometer \Pi`e*zom"e*ter\, n. [Gr. ? to press + -meter: cf. F.
   pi['e]zom[`e]tre.]
   1. (Physics) An instrument for measuring the compressibility
      of liquids.

   2. (Physics) A gauge connected with a water main to show the
      pressure at that point.

Source : WordNet®

piezometer
     n : a measuring instrument for measuring high pressures