2. This is a novel about frontier in the United States. 这是一部描写美国边界居民生活的小说。
3. To settlers on the frontier, Jackson was already well known. 对移居者在边境,杰克逊已经是知名的。
英英解释
n.
1. a wilderness at the edge of a settled area of a country
2. an international boundary or the area (often fortified) immediately inside the boundary
3. an undeveloped field of study; a topic inviting research and development