This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. A passage underneath something, especially a section of road that passes under another road or a railroad.

n. An intersection formed in this way.

n. A road or a pedestrian passage in a tunnel that runs underneath a road or railroad.

n. an underground tunnel or passage enabling pedestrians to cross a road or railway

"In New York, where I live now, such places are everywhere — a train underpass, a rooftop, a quiet street."

tunnel   

overpass   

subway   

round-arched    handcar    employé    prearrangement    speed    trackage    overpass    cantilever    centre    boxcar