passer vs passer-by

passer and passer-by both are nouns.

Word	Noun	Adjective	Verb	Adverb
passer	Yes	No	No	No
passer-by	Yes	No	No	No

As nouns, passer and passer-by are synonyms defined as:

Other synonyms of passer include passerby.

passer (noun)	passer-by (noun)
(football) a ball carrier who tries to gain ground by throwing a forward pass	a person who passes by casually or by chance
a person who passes by casually or by chance
a student who passes an examination
a person who passes as a member of a different ethnic or racial group