Lopper's Decapitation (Su), when?

[Mr. Microscope]

In the AP, it simply states that, "a creature slain by the Lopper's incorporeal touch is always decapitated."

What does, "slain" mean here? Below zero HP, or below -CON HP?

I don't want to chop off someone's head prematurely.

Thanks!

[Rysky]

Slain means dead, when their Negative HP is equal to their CON.

[Mr. Microscope]

Thank you!

[Rysky]

Np :3