| 31. | frontier defense |
| 边防
|
| 32. | a border [boundary, frontier ] dispute |
| 边界争端
|
| 33. | smuggle goods across a frontier |
| 将货物走私过境
|
| 34. | the frontier spirit |
| (美）拓荒精神
|
| 35. | mass troops on the frontier |
| 在边境上集结部队
|
| 36. | a border [ frontier ] violation |
| 对国境的侵犯
|
| 37. | advance the frontier of human knowledge |
| 扩大人类知识的领域
|
| 38. | close the frontier |
| 封锁边境
|
| 39. | delimit [demarcate] a frontier |
| 划定边界
|
| 40. | pacify the northwestern frontier |
| 平定西北边境
|