1. European thistle naturalized in United States and Canada where it is a pernicious weed. 美国和加拿大已引入的欧洲蓟，它是一种有害的杂草。
2. It is even more pernicious in the interface because it immediately makes the user feel incapable of using the product. 界面上的此类问题甚至更加有害，因为用户立刻就会感觉到他们无法使用这个产品。
3. The infection of disillusionment was surely the most pernicious disease of all, and he would not expose the others to it. 幻灭景象对心灵的感染实在是最危险的疾患，他不想让别的同伴也受到这样的伤害。
英英解释
adj.
1. exceedingly harmful
2. working or spreading in a hidden and usually injurious way
