The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

This can happen in signed and unsigned cases.

"Integer underflow" is sometimes used to identify signedness errors in which an originally positive number becomes negative as a result of subtraction. However, there are cases of bad subtraction in which unsigned integers are involved, so it's not always a signedness issue.

"Integer underflow" is occasionally used to describe array index errors in which the index is negative.