life belt

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

• noun A life preserver worn like a belt.

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

• noun A buoyant inflatable ring carried onboard ships which can be thrown to someone in the water in an emergency to keep themselves afloat.

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

• noun belt attaching you to some object as a restraint in order to prevent you from getting hurt
• noun a life preserver in the form of a ring of buoyant material