The actual term "key" is not used, but rather acceptable subcontractors (ISO 4.6.2c). The section describes the evaluation and approval of subcontractors. Therefore, the definition is "those subcontractors your company and/or the customer (let's not forget customer specified subcontractors) deemed as acceptable to be a source to purchase product from."
4.6.2.c specifically states that "Methods other than an "approved subcontractor list" may be utilized to meet the this requirement." This differs from ISO where the list is a requirement. What is important is that you have a documented method of determining which suppliers are acceptable and that you use it. You may find that the list is the easist method to use in your environment, but it is not a QS requirement.
KEY Supplier - QS-9000 Approved Suppliers - Definition of
Linear Mode
