cloak-and-dagger vs undercover

cloak-and-dagger and undercover both are adjectives.

Word	Noun	Adjective	Verb	Adverb
cloak-and-dagger	No	Yes	No	No
undercover	No	Yes	No	No

As adjectives, cloak-and-dagger and undercover are synonyms defined as:

cloak-and-dagger and undercover: conducted with or marked by hidden aims or methods

Other synonyms of cloak-and-dagger include clandestine, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, underground.

cloak-and-dagger (adjective)	undercover (adjective)
conducted with or marked by hidden aims or methods	conducted with or marked by hidden aims or methods