A building or other place that is impregnable is so strongly built and/or defended that it cannot be entered by force.

Despite burglar alarms and window locks, homes are never impregnable against determined thieves. 即使家里装上防盗警报器并锁好窗户，也挡不住贼心不死的小偷。

powerful and impossible to beat, especially in sport

Surrey have been building up an impregnable lead in this season's County Championship. 在本赛季的全郡锦标赛中，萨里队已经遥遥领先，势不可当。