* A misspelling: Perhaps you meant a different word, like "illusion" or "illusions."
* A made-up word: It could be a fictional language created for a specific purpose, like a book or game.
* A slang term: It might be a regional or subcultural slang term that isn't widely known.
Could you provide more context?
* Where did you encounter this word?
* What was the context of its use?
This information might help me figure out what "ilusm" actually refers to.