The Collaborative International Dictionary of English v.0.48:

Pluviometer \Plu`vi*om"e*ter\, n. [L. pluvia rain + -meter: cf.
   F. pluviom[`e]tre.]
   An instrument for ascertaining the amount of rainfall at any
   place in a given time; a rain gauge.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pluviometer
    n 1: gauge consisting of an instrument to measure the quantity
         of precipitation [syn: rain gauge, rain gage,
         pluviometer, udometer]