tracer bullet vs tracer

tracer bullet and tracer both are nouns.

Word	Noun	Adjective	Verb	Adverb
tracer bullet	Yes	No	No	No
tracer	Yes	No	No	No

As nouns, tracer bullet and tracer are synonyms defined as:

tracer bullet and tracer: ammunition whose flight can be observed by a trail of smoke

tracer bullet (noun)	tracer (noun)
ammunition whose flight can be observed by a trail of smoke	ammunition whose flight can be observed by a trail of smoke
	(radiology) any radioactive isotope introduced into the body to study metabolism or other biological processes
	an instrument used to make tracings
	an investigator who is employed to find missing persons or missing goods