The end line is a term that typically refers to the final boundary of a playing field or court. However, there are a variety of antonyms for the word "end line" that can be used to describe different types of boundaries or areas. For example, a synonym for "end line" could be "start line," which might describe the initial boundary of a racecourse or track. Alternatively, a different antonym might be "midline" or "center line," which could describe the dividing line that separates two different areas of a court or field. Other possible antonyms for "end line" might include "goal line," "side line," or "touch line," each of which refers to a different type of boundary that is used in various sports or activities.