"Unasking" the question
The term is often used or translated to mean that the question itself must be "unasked": no answer can exist in the terms provided. Zhaozhou's answer, which literally means that dogs do not have Buddha nature, has been interpreted by Robert Pirsig and Douglas Hofstadter to mean that such categorical thinking is a delusion, that yes and no are both right and wrong.
In Robert M. Pirsig's 1974 novel Zen and the Art of Motorcycle Maintenance, mu is translated as "no thing", saying that it meant "unask the question". He offered the example of a computer circuit using the binary numeral system, in effect using mu to represent high impedance:
For example, it's stated over and over again that computer circuits exhibit only two states, a voltage for "one" and a voltage for "zero." That's silly! Any computer-electronics technician knows otherwise. Try to find a voltage representing one or zero when the power is off! The circuits are in a mu state.
The word features prominently with a similar meaning in Douglas Hofstadter's 1979 book, Gödel, Escher, Bach. It is used fancifully in discussions of symbolic logic, particularly Gödel's incompleteness theorems, to indicate a question whose "answer" is to
"Mu" may be used similarly to "N/A" or "not applicable," a term often used to indicate the question cannot be answered because the conditions of the question do not match the reality.