What does that mean if a guy can't stop staring at you till you stop staring once he starts doing it?

It mostly means he's intreasted in you . The more you ingnore him the more he will stare if your not intreasted tell him to "go away " nicely.If you are intrested take it slow nd get to know him after all if he is staring at you now then you don't know what kind of creep he could be.

It's that or you have done something really embarissing in front of him so he is looking at you and laughing inside.