Rubbish consists of unwanted things or waste material such as used paper, empty tins and bottles, and waste food.

If you think that something is of very poor quality, you can say that it is rubbish .

If you think that an idea or a statement is foolish or wrong, you can say that it is rubbish .

If you think that someone is not very good at something, you can say that they are rubbish at it.

If you rubbish a person, their ideas or their work, you say they are of little value.