The term "aliquot divisor" is commonly used to mean two distinct but related things.
The first definition is a number that divides another exactly. For instance, 1, 2, 3, and 6 are aliquot divisors of 6. In this sense, "aliquot divisor" is the same as the usual divisor. A number that is not an (aliquot) divisor is said to be an aliquant divisor.
The term "aliquot" is also frequently used to specifically mean a proper divisor, i.e., a divisor of a number other than the number itself. For example, the aliquot divisor in this sense of 6 are 1, 2, and 3.