If you are uncertain about something, you do not know what you should do, what is going to happen, or what the truth is about something.
He was uncertain about his brother's intentions.
他不清楚他兄弟的意图。
They were uncertain of the total value of the transaction.
他们不清楚这笔交易的总额。
If something is uncertain, it is not known or definite.
How much practical help they can give us is uncertain.
他们能给我们多少实际帮助还是个未知数。
It's uncertain whether they will accept the plan.
还不知道他们是否会接受这项计划。
in no uncertain terms
If you say that someone tells a person something in no uncertain terms, you are emphasizing that they say it strongly and clearly so that there is no doubt about what they mean.
She told him in no uncertain terms to go away.
她非常明确地叫他走开。