Mountain bike. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/MOUNTAIN-BIKE
(plural mountain bikes)
A bicycle specially designed for off-road riding, typically with straight, flat handlebars, a heavier frame than road bikes, higher ground clearance, and wider tires, sometimes with knobs on them for greater traction.
English Wiktionary. Available under CC-BY-SA license.