In Six Sigma, a defect is defined as the failure of a product or service to meet customer Specifications or requirements. Thus, a 'defect' is customer-defined.
The 'customer' could be internal or external to the company. For instance, the customer could be the engineering department which lays down the engineering Specifications for the product.
There may be multiple defects per product or service. The number of defects can be converted to defects per million opportunities (DPMO) which is then used to determine a quality metric called the ‘sigma level’ of the process. A process with a sigma level of 6 produces on average only 3.4 DPMO.
Arrived late, did not have appropriate tools, could not identify root cause of problem: three defects in a house service call.