mountain bike 
noun
A bicycle with a light sturdy frame, broad deep-treaded tyres, and multiple gears, originally designed for riding on mountainous terrain.The reason for this was that she had her mountain bike in top gear....
- While walking by the perimeter fence of the playing fields, she noticed a man riding past on a mountain bike.
- I try to get out on my mountain bike or racing bike as much as I can.
Derivatives
mountain biker
- Since then he has become an avid road cyclist and budding mountain biker.
- Evans, a former mountain biker and the first Australian to wear the pink jersey, held the overall lead for just one day.
- At the age of 14 I used to work one day a week at a bike shop in Scarborough and I'm a keen mountain biker today.
mountain biking
- The championships will host several competitions, ranging from road racing to mountain biking.
- You can make mountain biking as challenging as you want to, varying your gears and route based on your ability.
- The many activities available nearby include fly-fishing, shooting, mountain biking, golf, and horse riding.