Not in the slightest is an idiomatic expression used to convey that something is not even a little bit true or relevant. This phrase can be replaced by several synonyms to add variety and clarity to your communication. Some of the synonyms for not in the slightest include not at all, not in the least, not in the minimum, not even slightly, not even nominally, not a shred, and not an iota. These synonyms can be used interchangeably depending on the context in which they are being used. So, next time when you want to express negation or deny something, you can use these synonyms instead of not in the slightest, to sound more articulate and refined.