storm drain vs storm sewer

storm drain and storm sewer both are nouns.

Word	Noun	Adjective	Verb	Adverb
storm drain	Yes	No	No	No
storm sewer	Yes	No	No	No

As nouns, storm drain and storm sewer are synonyms defined as:

storm drain and storm sewer: a system of watercourses or drains for carrying off excess water

Other synonyms of storm drain include drain system, drainage well, stormwater drain.

storm drain (noun)	storm sewer (noun)
a system of watercourses or drains for carrying off excess water	a system of watercourses or drains for carrying off excess water