main belt

Short definition from Wiktionary

Proper noun

1. 1
   Synonym of asteroid belt; the main asteroid belt in the Solar System located roughly between the orbits of the planets Mars and Jupiter.
2. 2
   Alternative letter-case form of main belt.

Noun

1. 1
   The primary belt of armor protecting the sides of a warship above and slightly below the waterline.
2. 2
   Alternative form of main belt.