seat belt vs life belt

seat belt and life belt both are nouns.

Word	Noun	Adjective	Verb	Adverb
seat belt	Yes	No	No	No
life belt	Yes	No	No	No

As nouns, life belt is a hypernym of seat belt; that is, life belt is a word with a broader meaning than seat belt:

seat belt: a safety belt used in a car or plane to hold you in your seat in case of an accident
life belt: belt attaching you to some object as a restraint in order to prevent you from getting hurt

Other hypernyms of seat belt include safety belt, safety harness.

seat belt (noun)	life belt (noun)
a safety belt used in a car or plane to hold you in your seat in case of an accident	a life preserver in the form of a ring of buoyant material
	belt attaching you to some object as a restraint in order to prevent you from getting hurt