Guilty secret noun phrase
A thing is known about by only a few people and kept hidden from others because it makes somebody feel ashamed.
You promised me that you wouldn't tell anyone about my guilty secret.
Once your guilty secret is out, your career will be ruined.
Lisa must carry this guilty secret for her whole life.
To be secretly working together
A person who contributes important work to the organization but is kept secret.
To secretly punish or rebuke someone for doing something.
Used to indicate the way someone does or something happens is secretive and quick
Do something silently, secretly.