Entry 1 sense Webster, 1913 Pluviometer · Plu·vi·om·e·ter · IPA /ˌplʊviːˈɑ.mɪ.tɚ/ 01 n. An instrument for ascertaining the amount of rainfall at any place in a given time; a rain gauge. 1. An instrument for ascertaining the amount of rainfall at any place in a given time; a rain gauge.