When you sweep or brush something under the carpet, you attempt to hide something embarrassing from others. Instead of dealing with your problem, you try to keep it a secret. It is also possible to say `sweep something under the mat/rug’.
Examples: The Government has managed to sweep the cola controversy under the carpet. *The actor tried to sweep the embarrassing incident under the rug.
Where does this expression come from? What is it that lazy people normally do when they are asked to clean a carpeted room? They sweep around the carpet, and instead of bending down to collect the dust, they quietly sweep it under the carpet!