Synonyms of clandestine

adjectiveDone or kept in secret, sometimes to conceal an illicit or improper purpose.

• covert
• furtiveOf a thing: done with evasive or guilty secrecy.
• hush-hushSecret, not spoken of (or spoken of only in hushed whispers between insiders).
• secret
• secretive
• undercover
• abstruseConcealed or hidden; secret.
• behind the scenes
• catlike
• backroom
• backstairs
• stealth slang
• cloak-and-daggerMarked by menacing furtive secrecy, often with a melodramatic tint or espionage involved.
• concealedHidden.
• confidential
• deep-laidSecret and carefully planned.
• dernHidden; secret; private.
• disguised
• huggermugger
• inconspicuous
• incognitoWithout being known; in an assumed character, or under an assumed title; in disguise.
• low profileAn intentionally furtive position as to not arouse suspicion or catch attention.
• lurksomeCharacterised or marked by lurking; lurky.
• lurkyTending to lurk; given to or indicative of lurking.
• mousy
• obfuscated
• off-the-books
• on the down-low
• on the slySlyly, in an inconspicuous manner, so as not to be seen; secretly; stealthily.
• slinky
• sly
• sneaky
• stealthyCharacterized by or resembling stealth or secrecy.
• sub rosaCarried out confidentially or secretly.
• surreptitiousStealthy, furtive, well hidden, covert (especially movements).
• under-the-table
• under the radarWithout attracting notice; in an undetected or secretive manner.
• under wraps
• undergroundHidden, furtive, secretive.
• unperceivedNot perceived.