Mainly used to say there is something that was decided shouldn’t be known by everyone.

An example was the actor Rock Hudson being gay. That was hidden from his fans and public until no one could hide he was dying of AIDS – his “skeleton in the closet” was made public.

And it wouldn’t be a very good proverb. There would be no real full context denoting a life lesson.

RE:
skeletons in the closet….definition?
All along, I have always understand this phrase as keeping secrets that you do not want people to know but recently, my friend said that it could only be used for family secrets…

is that true?

by the way, can it be considered as a proverb?

implies that you have murdered people and hid them in your closet.

It means a bad thing has been done and you have concealed it.

And no………..it is not restricted to family secrets.

Politicians who run for office are frequently found to have ‘skeletons in the closet’. Past marital affairs, drug use, participation in anti-patriotic demonstrations, avoiding the draft, ………………many things.

It means a juicy piece of bad stuff you did that you have managed to keep secret for a long long time.

No, it’s not a proverb. A proverb is a story that teaches a lesson. It’s a saying.