What is undefining?

In programming, undefining refers to removing the value or definition of a variable or constant. This means that the variable or constant no longer has a value assigned to it, or it is no longer defined in the program. Undefining a variable or constant is useful in certain situations, such as when reusing variable names or clearing the value of a variable between different functions. In some programming languages, such as JavaScript, the "undefined" keyword can be used to explicitly set a variable or constant to have no value.