clandestine
Definitions
Kept secret or done secretively, especially because illicit.
Conducted with or marked by hidden aims or methods.
Examples
The two spies held a clandestine meeting in the back of the dimly lit cafe.
They maintained a clandestine relationship for years, keeping their love hidden from the public eye.
The organization operated a clandestine network to smuggle supplies across the border.
Synonyms
secret covert surreptitious stealthy furtive underground hidden