life belt vs lifesaver

life belt and lifesaver both are nouns.

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

As nouns, life belt and lifesaver are synonyms defined as:

life belt and lifesaver: a life preserver in the form of a ring of buoyant material

Other synonyms of life belt include life buoy, life ring.

life belt (noun)	lifesaver (noun)
a life preserver in the form of a ring of buoyant material	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	an attendant employed at a beach or pool to protect swimmers from accidents