constant eye contact means a lot. if it is held for more than feels right, it definitely means something. when someones holds eye contact with you for longer than social etiquette dictates, then that person is flirting with you and ultimately wants you to approach them.
What Girls Said 1
Usually, eye contact is considered flirting when it's held for more than just a couple of seconds or so. I mean, would you spend more than a few seconds looking at someone's eyes if you weren't interested in them? My guess is probably not. But, if you like someone you wouldn't mind spending an extra bit of time looking into their eyes would you?
Also, trust your gut when you want to determine whether someone is just making eye contact to be polite or whether it's something more.