&gt;The question is, what is harassment?

This is a really common objection to anti-harassment measures, and it always has a really simple answer.  In a professional setting, don’t ask a woman for anything you wouldn’t ask a man for. If you wouldn’t ask a male colleague you don’t know well out for drinks, just the two of you, then apply the same standard to all of your coworkers.  If you wouldn’t tell a male coworker you like his physical appearance, don’t tell female coworkers you like their physical appearance.  It’s not a compliment, if it’s a sexual advance.

This does assume a certain level of men being reasonable.  If you have close friends at work, and it wouldn’t be weird for you to ask them out for drinks, then obviously it wouldn’t be weird.  If you don’t know what’s reasonable or not, see rule 1: don’t hit on people at work.

It’s really not hard.