The phrase "not a bit" expresses the absence of something and is typically used in negative statements. There are several synonyms for "not a bit" that can be used to convey a similar meaning. For example, "not at all" is another commonly used phrase that indicates the absence of something. "Nothing" and "no way" also express negation and can be used in place of "not a bit." Other synonyms for this phrase may include "not in the slightest," "absolutely not," and "by no means." These alternatives can add variety to your writing and help you communicate your message more effectively.