If you are unprepared for something, you are not ready for it, and you are therefore surprised or at a disadvantage when it happens.
双语例句
例： I was totally unprepared for the announcement on the next day.
我对次日的通告毫无准备。
例： Faculty members complain that their students are unprepared to do university-level work.
大学教师们抱怨他们的学生没有为大学阶段的学习打好基础。