life preserver vs flotation device

life preserver and flotation device both are nouns.

Word	Noun	Adjective	Verb	Adverb
life preserver	Yes	No	No	No
flotation device	Yes	No	No	No

As nouns, life preserver and flotation device are synonyms defined as:

life preserver and flotation device: rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning

Other synonyms of life preserver include preserver.

life preserver (noun)	flotation device (noun)
rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning	rescue equipment consisting of a buoyant belt or jacket to keep a person from drowning