When you point out something to make someone else look quickly, but what you said was there really isn't. It is only a broken neck if the person turns their head to look at it. If you did break their neck, then you place your hand on the back of their neck and "run it". If you really look, but said you didn't and don't accept the fact that you got your neck broken, this is called being a Cowan or Matt Cowan
James: Oh my god, Stru, look! It's snowing outside.
Stru: *quickly looks but it is actually a bright sunny day*
James: Broke ya neck! *runs Stru's neck*
Cacioppo: Yo Cow! Is that Mark over at the basketball court?
Cowan: *looks towards the court and nobody is there*
Cacioppo: Damn! Broke ya neck!
Cowan: What the fuck are you talking about I didn't look at all!
Cacioppo: Ay..don't be a Cowan.