adj.坚不可摧的；不可战胜的
They will establish impregnable fortresses. 他们将建造坚不可摧的城堡。
The lofty walls of the castle seemed impregnable. 这座城堡的高墙似乎坚不可摧。
The lawyer won his case with an impregnable argument. 律师以无可辩驳的论据打赢了那场官司。
