- Behind closed doors
- Furtively
- in concealment
- In confidence
- incognito
- Intimately
- On the q.t.
- Facelessly
- incognito
- In an anonymous manner; without a name.
- Unidentified; incognito
- Unknown
- Unknown author
- Nameless; of unknown name; also, of unknown or unavowed
authorship; as, an anonymous benefactor; an anonymous pamphlet or
letter.