There are various synonyms for the word "wander off" that you can use depending on the context. If you want to describe someone who has gone astray, words like stray, meander and swerve may work well. For someone who has lost their way, consider using words like deviate, veer off course and get lost. If you are talking about someone who is lost in thought or daydreaming, words like drift, zone out and lose oneself may work well. Additionally, words like ramble, rove and explore can be used to describe someone who is wandering with a purpose or for pleasure.