Here's how CMS defines a fall.
A fall caught in time is still a fall on the MDS in Section J.
Here's the RAI user manual verbiage for defining what counts as a fall:
A. An episode where a resident lost his/her balance and would have fallen, were it not for staff intervention, is a fall. In other words, an intercepted fall is still a fall.
B. The presence or absence of a resultant injury is not a factor in the definition of a fall. A fall without an injury is still a fall.
C. When a resident is found on the floor, the facility is obligated to investigate and try to determine how he/she got there, and to put into place an intervention to prevent this from happening again. Unless there is evidence suggesting otherwise, the most logical conclusion is that a fall has occurred.
D. The distance to the next lower surface (in this case, the floor) is not a factor in determining whether or not a fall occurred. If a resident rolled off a bed or mattress that was close to the floor, this is a fall.