(1) A defect is any variation of a required characteristic which is far enough removed from its target so as to cause customer dissatisfaction.
(2) A product's or service's non-fulfilment of an intended requirement or reasonable expectation for use, including safety considerations. There are four classes of defects: class 1 very serious, leads directly to severe injury or catastrophic economic loss; class 2 serious, leads directly to significant injury or significant economic loss; class 3 major, is related to major problems with respect to intended normal or reasonably foreseeable use; class 4 minor, is related to minor problems with respect to intended normal or reasonably foreseeable use.
(3) An occurrence such as a blemish, scratch, burn, error, or omission that appears on an object. A defect does not necessarily make the object unusable or unacceptable.
(4) Any output of any process or business task that does not meet its intended performance target within some extent of acceptable variation. Also known as error.