overcrossing vs gangway

overcrossing and gangway both are nouns.

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

As nouns, gangway is a hyponym of overcrossing; that is, gangway is a word with a more specific, narrower meaning than overcrossing:

Other hyponyms of overcrossing include gangboard, gangplank, jet bridge.

overcrossing (noun)	gangway (noun)
a bridge designed for pedestrians	a temporary passageway of planks (as over mud on a building site)
	a temporary bridge for getting on and off a vessel at dockside
	passageway between seating areas as in an auditorium or passenger vehicle or between areas of shelves of goods as in stores