footbridge vs overcrossing

footbridge and overcrossing both are nouns.

Word	Noun	Adjective	Verb	Adverb
footbridge	Yes	No	No	No
overcrossing	Yes	No	No	No

As nouns, footbridge and overcrossing are synonyms defined as:

Other synonyms of footbridge include pedestrian bridge.

footbridge (noun)	overcrossing (noun)
a bridge designed for pedestrians	a bridge designed for pedestrians