plumber vs pipe fitter

plumber and pipe fitter both are nouns.

Word	Noun	Adjective	Verb	Adverb
plumber	Yes	No	No	No
pipe fitter	Yes	No	No	No

As nouns, plumber and pipe fitter are synonyms defined as:

plumber and pipe fitter: a craftsman who installs and repairs pipes and fixtures and appliances

plumber (noun)	pipe fitter (noun)
a craftsman who installs and repairs pipes and fixtures and appliances	a craftsman who installs and repairs pipes and fixtures and appliances