The phrase "lack of ambiguity" is used to describe a situation where there is no uncertainty or doubt as to the meaning of a particular statement or action. There are several synonyms for this phrase that can be used interchangeably, including: clarity, certainty, definiteness, precision, specificity, and unambiguity. These words all convey a sense of clarity and certainty, suggesting that there is no room for confusion or misinterpretation. In general, any phrase or word that emphasizes a clear and straightforward meaning or intention can be used as a synonym for "lack of ambiguity".