traffic jam vs snarl-up

traffic jam and snarl-up both are nouns.

Word	Noun	Adjective	Verb	Adverb
traffic jam	Yes	No	No	No
snarl-up	Yes	No	No	No

As nouns, traffic jam and snarl-up are synonyms defined as:

traffic jam and snarl-up: a number of vehicles blocking one another until they can scarcely move

traffic jam (noun)	snarl-up (noun)
a number of vehicles blocking one another until they can scarcely move	a number of vehicles blocking one another until they can scarcely move