I am interested in knowing what women interpret as a "do not approach" sign from men's behavior, demeanor, or appearance without him having to directly state to a woman that he is not interested and is not looking.

Assume that the guy in question is physically good looking, competent, socially skilled, and overall women think he would make a "good catch." What is it about him that a woman would interpret as a "this guy isn't interested?"

I know a guy who women are curious about, but when I ask these women how come they do not flirt or bother to approach him and make themselves available for him to approach them they just give me enigmatic replies like: "he looks like he wouldn't be interested" or "he's giving off 'no trespassing signs.'"

How do women know? Because the guy is my friend and I have asked him what's up with him, and women's instincts are correct, he doesn't like being approached and when we are out he really doesn't want to be bothered by women even though they all think he's good looking because he's tall, well dressed, and groomed and sociable.

I've asked him what the hell is he doing to broadcast his intentions without words and the only thing I got our of him is that he intentionally doesn't smile to women when they walk up to him and he keeps his answers brief, cold, but courteous until women just kinda take the hint and leave him alone. He says he figured out this is the best way to politely communicate that he's not interested.

So I am curious, is this really it? Just not smile, be robotic, and women just leave dudes alone?

Bear in mind he only does this with women that have romantic intentions. Like I said he's really sociable so he has a hard boundary that he doesn't let women cross, we have mutual female friends and they don't see any issues with him and they like him - just not in "that way" which is what he prefers.