What does it really mean when a guy grabs your ass?

I 'd never do it to a woman I don't date, but I like to do it.

I use to do it when I am hanging out with a girl I like, I have been making out with her but not sexually yet. It is a good place to start telling her that you are interested in something else and not asking it directly (which reduces the possibilities of success by the way). I think that girls find it less offensive than grabbing their breasts unexpectedly or other places, and you can do it easily while dancing or making out and while standing. I would definitely not do it to a girl I don't know or think in the inside that she is going to get mad about it. You have to take your chances though... :)

Pure sexual gratification, he either figures he'll get away with it, or he figures the brief thrill is worth a smack in the face.

It means that you have just been sexually assaulted and can now count yourself amongst those numbers.

it means the guy is looking to get slapped, maced, arrested, ect.
it doesn't matter if yor offended or turned on, it shows a lack of respect to you.

well I really don't think when I to do it, its just arousing lol but be a little more detailed, do you mean in public or Private cuzz I would never grab my girls ass in public (hate being the center of attention) but in private ill rub the hell out of it... why? Because to me (Meaning just me and possible to other guys) the ass is equivalent to boobs in the way that their fun to grab and look at for no reason at all other than sexual arousal.

this guy I've been seeing and having sex with does it when we go to the club together but does it when nobody sees it and I find it sexy... I think it's like saying ''I want you sexually''

If he's your ex and you've talked to him about how you no longer have feelings for him, then the next time he does it, flip your lid. Hard. Wig out on him and make him back off. Giggle at your vengeance later.
If you do still have those pesky feelings for him, then talk to him and ask him why he continues to push your buttons. Because there are chances that that's his immature way of saying he likes you and wants to get back together.

if he is ur boyfriend then he wants you sexually but if he isn't ur boyfriend then he should know his limits w u

That means that they can think they can do whatever they want to you and you won't get mad

I don't see it as a bad way when my boyfriend does it. He rarely does it anyways, so I know that when he does grab my ass, he is a little worked up/admiring my ass. That's how I see it ^^

NOW If it were a random stranger... I'd kick his ass >_>