Semantically it is comparable to answering “neither is true”, as in:
Do you have a sister or a brother?
The Japanese word “mu” (Kanji: 無, Hiragana: む) describes the absence of something. It may be translated as “nothing” or “without”. It is also a central concept in the philosophy of Zen where it is used to show the limitations of a dualist world-view.
- Mu (negative) on Wikipedia