What does that mean if the guy you like passes by you for like 4 times in a class and right before or after he passes by you he looks at you?

Either he really likes you, or he's a staring weirdo.

Probably means he's kinda nervous b/c he knows you like him and doesn't really know how to react and is trying to formulate a response or is trying to intimidate you to not like him anymore. Take your pick. There is also a small chance that he's just playfully messing with you.