‘Elephant in the room’
Meaning:An important topic that everyone present is aware of, but that is considered uncomfortable and is not being discussed
Explanation:Originating in the US, this phrase dates back to at least the 1950s and may have initially had a slightly different meaning to the one we use today. The current usage appears in the title of a 1984 book intended to help the children of alcoholics, and has since been used frequently to describe a subject that needs to be talked about but often isn’t.
Example: Global poverty was the elephant in the room at the latest political conference.