Definition [Cambridge Dictionary]:

1. To decide that something or someone is not important and not worth considering. [不理会、不考虑]

2. To remove someone from their job, especially because they have done something wrong. [解雇、开除]

3. To formally ask or order someone to leave. [让……离开]

4. When a judge dismisses a court case, he or she formally stops the trial, often because there is not enough proof that someone is guilty. [驳回、不受理]

Example:

Just dismiss those thoughts from your mind - they're crazy and not worth thinking about.

把这些想法从你的脑袋中去掉吧，它们太疯狂了，不值得考虑。

He has been dismissed from his job for incompetence.

他因不能胜任这份工作而被开除了。

The professor dismissed the class early because she had a meeting.

因为教授还有个会，所以早点下课了。

The defending lawyer asked that the charge against his client be dismissed.

辩护律师请求驳回对其委托人的指控。