scummy vs low-down

scummy is not a noun while low-down is a noun.

Word	Noun	Adjective	Verb	Adverb
scummy	No	Yes	No	No
low-down	Yes	Yes	No	No

As adjectives, scummy and low-down are synonyms defined as:

Other synonyms of scummy include abject, low, miserable, scurvy.

scummy (noun)	low-down (noun)
	slang terms for inside information

scummy (adjective)	low-down (adjective)
of the most contemptible kind	of the most contemptible kind
covered with scum	(of jazz) having the soulful feeling of early blues