piston vs plunger

piston and plunger both are nouns.

Word	Noun	Adjective	Verb	Adverb
piston	Yes	No	No	No
plunger	Yes	No	No	No

As nouns, piston and plunger are synonyms defined as:

piston and plunger: mechanical device that has a plunging or thrusting motion

piston (noun)	plunger (noun)
mechanical device that has a plunging or thrusting motion	mechanical device that has a plunging or thrusting motion
	hand tool consisting of a stick with a rubber suction cup at one end; used to clean clogged drains
	someone who risks losses for the possibility of considerable gains
	someone who dives (into water)