a BDSM toy, mostly seen in Japanese porn. It is basically a hook whose two rounded prongs are put inside a submissive's nostrils. The hook is then pulled towards the top of the head.
For a home made instant experience, just stick two fingers inside your nostrils and try to turn your nose into a pig snout. There you have it. I am not sure what is so fun about nose hooks, but the Japanese definitely love them.