hole-and-corner
1. [ adjective ] relating to the peripheral and unimportant aspects of life
Synonyms: hole-in-corner colorless
Examples:

"a hole-and-corner life in some obscure community"- H.G.Wells

Related terms: insignificant
2. [ adjective ] conducted with or marked by hidden aims or methods
Synonyms: secret clandestine undercover underground on_the_quiet hush-hush surreptitious hugger-mugger cloak-and-dagger
Examples:

"clandestine intelligence operations" "cloak-and-dagger activities" "secret missions" "surreptitious mobilization of troops" "an undercover investigation" "underground resistance"

Related terms: covert