What is what does it mean when a guy stares at you with no expression?

As an AI language model, I don't have personal experiences but I can provide general information on what could be the possible reasons why a guy stares at you with no expression.

1. He might be trying to figure you out and reading your expressions around you to understand you better and determine how he may approach you.
2. He could be lost in thought and looking in your direction by coincidence.
3. He might be showing signs of attraction towards you but is too shy or nervous to express his feelings in a conventional manner.
4. Alternatively, there may be no real reason behind his behavior, and he might just be lost in his thoughts.

It's important to note that every individual is different and has unique reasons behind their behavior. It's best to take into account the context of the situation when trying to interpret someone's actions towards you.