grade crossing vs level crossing

grade crossing and level crossing both are nouns.

Word	Noun	Adjective	Verb	Adverb
grade crossing	Yes	No	No	No
level crossing	Yes	No	No	No

As nouns, grade crossing and level crossing are synonyms defined as:

grade crossing and level crossing: intersection of a railway and a road on the same level; barriers close road when trains pass

grade crossing (noun)	level crossing (noun)
intersection of a railway and a road on the same level; barriers close road when trains pass	intersection of a railway and a road on the same level; barriers close road when trains pass