to walk around slowly in a relaxed way or without any clear purpose or direction

We spent the morning wandering around the old part of the city. 我们整个上午都在老城区闲逛。

She was found several hours later, wandering the streets, lost. 几个小时后她被找到了，正在街上徘徊，迷路了。

He was here a minute ago but he's wandered off somewhere. 他刚才还在这儿，现在已经闲逛到别的什么地方去了。

to start talking about a different subject from the one you were originally discussing

We've wandered off/from the point somewhat. 我们有点离题了。

If your mind or your thoughts wander, you stop thinking about the subject that you should be giving your attention to and start thinking about other matters.

Halfway through the meeting my mind started to wander. 会开到一半时我就开始走神了。

If you say that an old person's mind is beginning to wander, you mean that they are starting to get very confused because of their age.

Her mind is beginning to wander and she doesn't always know who I am. 她的神志开始恍惚，有时认不出我是谁。