The antonyms for the phrase "tips off" can include phrases such as "remains silent," "withholds information," "stays mum," and "keeps mum." When someone tips off, it means that they reveal or give away information, often confidential or secretive. In contrast, if someone remains silent or withholds information, they are not revealing anything, and they are keeping information to themselves. These antonyms may be useful in situations where someone is trying to keep something confidential or when they do not want to give away any information that could compromise the safety or privacy of others.