bullet vs heater

bullet and heater both are nouns.

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

As nouns, bullet and heater are synonyms defined as:

Other synonyms of bullet include fastball, hummer, smoke.

bullet (noun)	heater (noun)
(baseball) a pitch thrown with maximum velocity	(baseball) a pitch thrown with maximum velocity
a projectile that is fired from a gun	device that heats water or supplies warmth to a room
a high-speed passenger train