life belt vs seatbelt

life belt and seatbelt both are nouns.

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

As nouns, seatbelt is a hyponym of life belt; that is, seatbelt is a word with a more specific, narrower meaning than life belt:

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

Other hyponyms of life belt include seat belt.

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