Sudden, urgent, usually unexpected occurrence or event requiring immediate action.
Note 1 to entry: An is usually a disruption or condition that can often be anticipated or prepared for, but seldom exactly foreseen.

Coordination across state agencies, local authorities, private entities, and volunteer organisations is needed in developing crisis communications and information management documentation and procedures.
First definition is the default one that is used in DRIVER+. Further definitions (if any) are the ones commonly used in specific sub-communities with relevance to the Crisis Management.