What does the Korean word oni mean?

The Korean word "oni" (오니) doesn't exist in the standard Korean language. It's likely you're thinking of the Japanese word "oni" (鬼), which translates to demon or ogre.

If you're looking for a Korean equivalent, you could use words like:

* 귀신 (gwisin): This is the most common word for "ghost" or "spirit".

* 요괴 (yogye): This word refers to a supernatural being, similar to a demon or monster.

* 악마 (akma): This word means "devil".

It's important to note that the specific connotation of these words can vary depending on the context.