Final answer:
A disaster is an event that causes a Critical Business Function to stop operating beyond the maximum tolerable downtime, often resulting from environmental disturbances or human activities and representing a significant economic risk.
Step-by-step explanation:
An disaster is an event that prevents a Critical Business Function (CBF) from operating for a period greater than the maximum tolerable downtime. Disasters can be the result of environmental disturbances such as natural disasters or human activities which lead to a significant disruption in the business operations. It is an economic risk over which individuals and businesses may have very little control. Ensuring that contingency plans and strategies are in place to mitigate these risks is crucial for the continuity and survival of the business.