An integer that is not a whole number is a negative integer. Whole numbers are defined as all non-negative integers, which include zero and positive integers (0, 1, 2, 3, …). However, negative integers such as -1, -2, -3, etc., fall outside the category of whole numbers because they are less than zero.
In essence, integers encompass both positive and negative numbers, along with zero, but whole numbers only refer to the positive side of the number line along with zero. Therefore, any negative integer serves as an example of an integer that is not a whole number.