to stop being directed on something and to move without much control to other ideas, subjects, etc.
پرسه زدن, بی هدف حرکت کردن, سرگردان شدن
It's easy to be distracted and let your attention wander.
Try not to let your mind wander.
Her thoughts wandered back to her youth.
Don’t wander off the subject—keep to the point.
synonym drift