A mountain bike or mountain bicycle (abbreviated MTB or ATB (all-terrain bicycle)) is a bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

 created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines,
on dirt trail

Trail

A trail is a path with a rough beaten or dirt/stone surface used for travel. Trails may be for use only by walkers and in some places are the main access route to remote settlements...

s, logging roads, and other unpaved environments—activities usually called mountain biking

Mountain biking

Mountain biking is a sport which consists of riding bicycles off-road, often over rough terrain, using specially adapted mountain bikes. Mountain bikes share similarities with other bikes, but incorporate features designed to enhance durability and performance in rough terrain.Mountain biking can...

. These bicycles need to be able to withstand the stresses of off-road use with obstacles such as logs and rocks.