low-down vs abject

low-down is a noun but abject is not a noun.

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

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

Other synonyms of low-down include low, miserable, scummy, scurvy.

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

low-down (adjective)	abject (adjective)
of the most contemptible kind	of the most contemptible kind
(of jazz) having the soulful feeling of early blues	showing utter resignation or hopelessness
	showing humiliation or submissiveness
	most unfortunate or miserable