If you are unprepared for something, you are not ready for it, and you are therefore surprised or at a disadvantage when it happens.
I was totally unprepared for the announcement on the next day.
我对次日的通告毫无准备。
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。
If you are unprepared to do something, you are not willing to do it.
They are unprepared to accept the real reasons for their domestic and foreign situation.
他们不愿接受造成其国内外形势的真正原因。