noun 下载 🔗分享 拱石,楔形石。 One of a series of wedge-shaped bricks or stones forming an arch or vault. Examples : "The keystone locked all the voussoir securely in place, completing the arch over the doorway. " 拱顶石将所有拱石牢固地锁定到位,完成了门道上方的拱形结构。 architecture building 与AI对话词汇游戏阅读练习