1. Abbreviated as, Mt. or Mtn.; a natural elevation of the earth's surface having considerable mass, generally steep sides, and a height greater than that of a hill.
2. A natural elevation of the earth's surface rising more or less abruptly to a summit, and attaining an altitude greater than that of a hill, usually greater than 2000 ft. (610 m).
3. A large heap: a mountain of laundry; a huge quantity: a mountain of trouble.

Living spaces for plants and animals as part of high places which rise as high as five and a half miles (nine kilometers) above sea level and have several different environments: "Each height can have several mountain habitats from temperate woodland on up to arctic conditions as climate changes take place when going up to higher altitudes."