Emergency

Noun

1. A situation which poses an immediate risk and which requires urgent attention.

   "Cardiac arrest is an emergency requiring medical attention."

2. The department of a hospital that treats emergencies.
3. A person brought in at short notice to replace a member of staff, a player in a sporting team, etc.
4. The quality of being emergent; sudden or unexpected appearance; an unforeseen occurrence.
5. A critical urge to urinate or defecate.