noun

• A situation which poses an immediate risk and which requires urgent attention.
• The department of a hospital that treats emergencies.
• An individual brought in at short notice to replace a member of staff, a player in a sporting team, etc.
• (attributive) Arising from or used in an emergency.
• (archaic) The quality of being emergent; sudden or unexpected appearance; an unforeseen occurrence.
• (historical, Ireland) World War II as experienced in Ireland.