This word gets thrown around a lot, and I think everyone uses it a little differently, which is one of the reasons why I have so much difficulty putting it into words. Let me try with: If you approach me with the presumption, stated or implied, that I owe you anything -- my time, my attention, my energy, my conversation, my acquiescence to your desires -- that's entitlement. If you make me think that you think you can express a wish and I will fulfill that wish, that's entitlement.

Women don't owe you anything: not their bodies, not their time, not their emotion. Hell, not even their attention. (Nobody owes anybody anything except basic courtesy, respect, and trying not to be an asshole.) A lot of guys walk into a situation and give the impression that they have the right to take these things, through outright force or through a more subtle coercion. Giving someone that impression makes you That Guy.