asteroid belt

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

• noun The region of the solar system between the orbits of Mars and Jupiter, where most of the asteroids are found.

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

• noun astronomy The region of the orbital plane of the solar system located between the orbits of Mars and Jupiter which is occupied by numerous minor planets and the dwarf planet Ceres.

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

• noun the region of interplanetary space between Mars and Jupiter where most asteroids are found