There may be a number of definitions of defect. However, there is a common interpretation among the dictionaries.
A lack of something necessary or desirable for completeness, adequacy or perfection.
When it comes to manufacturing, what is necessary to a product is usually documented into product specifications. Besides, what is desired by product users can be interpreted as user expectations. Therefore, defect can be translated into the following definition.
Non-conformance of a product with the specified requirements, or non-fulfillment of user expectations.
As we can see from these definitions, defect is closely associated with the actual behaviour or features of a product and its user expectations. Therefore, we could safely interpreted defect as:
The deviation of actual from expected behaviour or features of a product.
