surreptitious Synonyms

furtive sneaky underground secret cloak-and-dagger stealthy clandestine hole-and-corner hush-hush undercover hugger-mugger sneak stealthful sneaking sly slinky slinking skulking under false pretense subreptitious subterrestrial under cover conspiratorial under-the-table sub-rosa wily veiled underhanded underhand treacherous subtle sideways sidelong shrouded deceitful cunning crafty covinous covert confidential concealed closet backstair backstairs backhanded backdoor devious disguised shifty secretive