A skeleton in the cupboard/closet noun phrase
An embarrassing or unpleasant secret about your past that you don't want anyone to know
It seems that most people have their own skeletons in the cupboard.
The press is really good at uncovering skeletons in the celebrities’ closets.
I know that friends should share with each other but there're some skeletons in the cupboard better to keep for myself.
My first failed love confession is my skeleton in the cupboard.
Used to tell someone to keep secret what you're about to say
To be secretly working together
Kept in secret
Someone who is totally bad at doing something.
Mary really can't sing for toffee.