rain gauge vs udometer

rain gauge and udometer both are nouns.

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

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

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

Other synonyms of rain gauge include pluviometer, rain gage.

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