Source : Webster's Revised Unabridged Dictionary (1913)

Udometer \U*dom"e*ter\, n. [L. udus wet, moist + -meter.]
   (Meteor.)
   A rain gauge.

Source : WordNet®

udometer
     n : gauge consisting of an instrument to measure the quantity of
         precipitation [syn: {rain gauge}, {rain gage}, {pluviometer}]