Source : Webster's Revised Unabridged Dictionary (1913)

Atmometer \At*mom"e*ter\, n. [Gr. ? smoke, vapor + -meter: cf.
   F. atmom[`e]tre.]
   An instrument for measuring the rate of evaporation from a
   moist surface; an evaporometer. --Huxley.

Source : WordNet®

atmometer
     n : an instrument that measures rate of evaporation of water
         [syn: {evaporometer}]