udometer vs rain gage

udometer and rain gage both are nouns.

Word	Noun	Adjective	Verb	Adverb
udometer	Yes	No	No	No
rain gage	Yes	No	No	No

As nouns, udometer and rain gage are synonyms defined as:

udometer and rain gage: gauge consisting of an instrument to measure the quantity of precipitation

Other synonyms of udometer include pluviometer, rain gauge.

udometer (noun)	rain gage (noun)
gauge consisting of an instrument to measure the quantity of precipitation	gauge consisting of an instrument to measure the quantity of precipitation