The meaning of "out"

Dear native English speakers,

I have a question about the usage of "out" in the following sentence.
What does it mean?

The professor was glaring out from behind the pile of exams when the tardy student approached him, almost 15 minutes later, with his exam clutched behind his back.

Thanks in advance.

Hirashin

I would think it means one of two things. One is that the pile is so high that he has to change his perspective to see what he is looking at. Or number two being more likely, is that he is very absorbed in what he is doing. It could also mean like outward, in otherwards he is scanning the room not looking in a particular direction. That is the only meanings I can think for it in that context.

Thanks for your help, OoTmaster.

I'll give you the other parts of the passage in case you need to judge it.

"You will have exactly two hours," said the professor as he handed out examination papers to a roomful of students. "Under no circumstances will I accept a paper given to me after the deadline has passed." Two hours later he broke the silence. "Time is up," he said. But one student continued to work furiously.
The professor was glaring out from behind the pile of exams when the tardy student approached him, almost 15 minutes later, with his exam clutched behind his back. When the professor refused to accept it, the student drew himself up to full stature and asked,
"Professor, do you know me?"
"No," said the professor.
"Terrific," replied the student, and he stuffed his paper into the middle of the pile.

Hirashin

Good joke.

I think it has similer meaning to "looking out the window". The professor is in a kind of cubicle/house made by his desk and the files piled on the desk so he is glaring/looking out through the window/file piles at the student.

Uncle Frank

I agree with Frank. It has to do with the direction the professor is glaring (looking). He is surrounded by exams, and he is glaring out of them, to look beyond them. Had the sentence just said, "The professor was glaring from behind the pile of exams..." then it could be possible that the professor may have just been glaring at one of the exams or something (even though this sentence would be confusing and unnatural).

Thank you for the help, Frank and Clark.

So the "out" shows that the pile of exam papers is like a wall.

Hirashin

Exactly!

I got it. Thanks, Clark!