To make eye contact with someone of the opposite sex randomly for a extended amount of time without ever speaking. ( It doesn't matter the distance between the two people)

Literally everyone, ever. Including the writer of this definition.

to look at someone, and look away when they look back. then have someone look at you, and look away when you look back.

to flirt with a guy or girl using only your eyes, usually across a crowded room or area ie a party