How is 'Kuronue' spelled in kanji?
His name is written 黒鵺（くろぬえ）according to the Japanese Wikipedia.

His name means "black chimera." The Japanese chimera is a mythical creature with a monkey's head, tanuki's body, tiger's limbs, and a snake tail.

If you do a Google search for 「黒鵺」, pretty much everything that comes up is about Yuu Yuu Hakusho.