Didst is an archaic form of the past tense of "do" or "did," which was commonly used in Middle English. The word has now become obsolete, and there are many synonyms that can replace it easily. Some common alternatives for Didst can be considered as "did," "performed," "accomplished," "fulfilled," "executed," and "carried out." Each of these synonyms conveys the same meaning as Didst and fits perfectly in a sentence, giving a modern and clearer meaning. Therefore, it's essential to choose the right substitute for the word according to the context and meaning of the sentence to ensure clear communication.