It means to live work in a way that causes you feel anxiety and worry.eg: Some people perform well under pressure and some others don't.Athletes must perform well under extreme pressure especially in big events such as Olympic Games. Note:Be under pressure的意思为在压力中紧张、担忧地工作或生活。例：有些人在压力中依然能正常发挥，有些人则不能。    运动员必须能克服压力，尤其是在奥林匹克这样的大型运动会中。