impregnable
adj. （要塞）坚固的，无法攻取的；不受影响的，难以改变的；可受孕的，可生育的
例句
The team built up an impregnable 5-1 lead.
这个队以5:1的绝对优势领先。
《牛津词典》
The old Dutch fort with its thick high walls looks virtually impregnable.
该座荷兰老城堡城墙又高又厚，看上去固若金汤。
《柯林斯英汉双解大词典》
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。
《新英汉大辞典》
