COMMON If someone is a bad apple or a rotten apple, they are very dishonest or unpleasant, and they have a bad influence on the people around them. It's an opportunity for them to make clear that they are not going to tolerate a bad apple in the United States Senate. In any profession, there's always the rotten apple, isn't there. Note: If a rotten apple is stored with good apples, it causes the good ones to rot.