"More rock-bound" refers to a place that is characterized by rocky terrain or surroundings. Its antonyms include terms like "lush," "fertile," and "green." These words describe areas with a lot of vegetation, such as forests or grasslands, as opposed to rocky areas that might not support much plant life. Other antonyms for "more rock-bound" might include words like "smooth," "sandy," or "flat," which describe areas that are not rocky, bumpy or hilly, but instead have a more even surface. In summary, antonyms for "more rock-bound" tend to emphasize vegetation, smoothness, softness and flatness.