There are several synonyms that can be used in place of the phrase "not in the least." These include "not at all," "not even slightly," "not in the slightest," and "not in the slightest degree." These phrases all convey the same meaning of complete and absolute negation. They can be used in a variety of contexts to express disinterest, lack of concern, or lack of belief. When used in conversation, it is important to choose the phrase that best fits the tone and intent of the conversation. Ultimately, using synonyms for "not in the least" allows for greater accuracy and emphasis in communication.