mountain range

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A series of mountain ridges alike in form, direction, and origin.

from The Century Dictionary.

• noun A range of mountains; specifically, in geology, the series of more or less parallel ridges formed over the area and border of a single anticlinal or synclinal mountain-fold considered as a unit.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A series of adjoining mountains, often in a line.
• noun A series of lines of mountains.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a series of hills or mountains