The antonyms for the phrase "wast subsequent to" are numerous, and they depend on the context in which the phrase is used. However, some common antonyms for "wast," meaning "was," include were, had been, and had existed. Opposites for "subsequent" could be previous, prior, or earlier. Therefore, antonyms for "wast subsequent to" could be stated as "had existed before," "were prior to," or "had been earlier than." Understanding the opposite meanings of words can help to provide clarity in communication and avoid confusion. It is necessary to pick the right antonyms based on the context used to avoid creating more confusion in a text.