The phrase "top heap" can be substituted with a variety of synonyms depending on the context. For example, "peak mound," "summit pile," and "crest stack" all convey a similar idea of the highest point or accumulation of something. Additionally, "apex mass," "zenith grouping," and "highest array" could be used to describe a top heap in a more formal or technical setting. In a more casual or colloquial context, "king pile," "champion stash," or "boss mound" might be more appropriate synonyms. Regardless of the word choice, the meaning of a top heap remains the same - a high or piled accumulation of something.