dead-end street vs cul de sac

dead-end street and cul de sac both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead-end street	Yes	No	No	No
cul de sac	Yes	No	No	No

As nouns, dead-end street and cul de sac are synonyms defined as:

Other synonyms of dead-end street include blind alley, impasse.

dead-end street (noun)	cul de sac (noun)
a street with only one way in or out	a street with only one way in or out
	a passage with access only at one end