slang expression vs slang word

slang expression and slang word both are nouns.

Word	Noun	Adjective	Verb	Adverb
slang expression	Yes	No	No	No
slang word	Yes	No	No	No

As nouns, slang expression and slang word are synonyms defined as:

slang expression and slang word: a word or expression that is outside of standard usage and is very informal

Other synonyms of slang expression include slang term.

slang expression (noun)	slang word (noun)
informal language consisting of words and expressions that are not considered appropriate for formal occasions; often vituperative or vulgar	a word or expression that is outside of standard usage and is very informal
a word or expression that is outside of standard usage and is very informal