* A misspelling: Perhaps you meant a different word, like "ru-ru" which could be a playful pronunciation of "ruru" similar to how we say "boo-boo" in English.
* A made-up word: Some people use made-up words for fun or artistic expression.
* A regional dialect: "Ruru" might be a word used in a specific region of Japan that isn't commonly used in standard Japanese.
If you provide more context, I might be able to help you understand what "Ruru" refers to. For example, where did you see or hear this word? Was it in a song, movie, or book?