What does it mean? Google says the guy is interested in you. There is this guy, with no known sexuality, that I really really like and sometimes when I look at him he raises his eyebrows at me (like a form of winking but with the eyebrows).
I've seen a few people do that to say "hi" instead of waving, but it probably is flirty if he does it twice, that's less usual. I don't know, I suck at reading body language