undercover Synonyms

clandestine hugger-mugger cloak-and-dagger underground secret hush-hush surreptitious hole-and-corner sub-rosa behind-the-scenes back channel unseen underneath underhanded stealthily stealthy underhand subterranean subterraneous undergrow secluded under wraps under the counter under cover top secret sneakily on the sly on the qt in disguise under-the-table surreptitiously confidentiality clandestinely in the dark unmarked camouflaged belowground stealthful stealth spial furtively furtive disguised covertly covert covered confidentially confidential concealed closet