The word "champaigns" is not often used in modern English but is defined as flat, open country. As such, some antonyms for this word could be rugged, rocky, mountainous or hilly terrain. Other antonyms might include areas with thick forests or dense vegetation, such as jungles or rainforests. In contrast, desert or barren landscapes with little to no vegetation could also serve as antonyms. Areas with steep cliffs or canyons could also be considered antonyms to champaigns. Essentially, any type of terrain that is not flat and open could be considered an antonym to the word "champaigns".