is the prevention of errors and adverse effects to patients associated with health care (WHO)

Patient safety culture: a culture that exhibits the following five high-level attributes that health-care professionals strive to operationalize through the implementation of strong safety management systems; (1) a culture where all health-care workers (including front line staff, physicians, and administrators) accept responsibility for the safety of themselves, their coworkers, patients, and visitors; (2) a culture that prioritizes safety above financial and operational goals (3) a culture that encourages and rewards the identification, communication, and resolution of safety issues; (4) a culture that provides for organizational learning from accidents; (5) a culture that provides appropriate resources, structure, and accountability to maintain effective safety systems

From:  Forum and End Stage Renal Disease Networks, National Patient Safety Foundation, Renal Physicians Association. National ESRD Patient Safety Initiative: Phase II Report. Chicago: National Patient Safety Foundation, 2001  [Described in: WHO Multi-professional patient safety curriculum guide (page 81)]

Is a conceptual model first described by James Reason, a professor of psychology, to explain the notion that an active error is usually not due to a single fault, either from an individual or a component in a system. Rather, it is often due to a series of faults (the analogy of the "holes" in the cheese, where all defenses in the  system are defeated) that momentarily line-up to allow for an error to pass through.

Reference:

Reason J. Human error: models and management. BMJ2000 Mar 18;320(7237):768-70.