Does The Joint Commission provide an official definition of a patient 'fall' or does each organization need to define it?

Any examples are for illustrative purposes only.

No, The Joint Commission does not have an official definition of a 'fall', however a uniform definition is needed throughout the organization.  Organizations are encouraged to check national guidelines (see "Additional Resources" below) and to check with their state to determine if any law/regulation exist defining a fall within the individual state.  The organization should choose a definition appropriate for the patient/client population served.

For consideration, a fall may be described as an unintentional change in position coming to rest on the ground, floor, or onto the next lower surface (e.g. onto a bed, chair or bedside mat). The fall may be witnessed, reported by a patient, an observer, or identified when the patient is found on the floor or ground. Falls include any fall whether it occurred at home, out in the community, in an acute hospital, or ambulatory setting.

Additional Resources
Sentinel Event Alert: Preventing Falls and Fall-related Injuries in Health Care Facilities
Targeted Solutions Tools for Preventing Falls
Agency for Healthcare Research and Quality AHRQ (enter falls in the search field)
Summary of the Updated American Geriatrics Society/British Geriatrics Society clinical practice for prevention of falls in older persons.": "Journal American Geriatric Society 2011 Jan.59(1):128-157