The word "indefinability" refers to something that cannot be defined or described clearly. There are several antonyms that can be used to express the opposite meaning. These antonyms include "clarity," "explicitness," "precision," "definition," "certainty," "concreteness," and "specificity." These words indicate that something is clear, precise, and well-defined. In contrast, the term "indefinability" implies vagueness, ambiguity, and a lack of clarity. By using appropriate antonyms, we can communicate our ideas more effectively, and ensure that our audience understands the meaning of our words clearly.