noun which may take the genitive case particle 'no', noun
for emergency use; emergency
Used as a noun or no-adjective to describe items, supplies, exits, or measures reserved for emergencies.
非常用の食料を備蓄している。
We stockpile emergency food supplies.
非常用の出口はこちらです。
The emergency exit is this way.
緊急用 also means 'for emergency use', but 緊急 emphasizes urgency, while 非常 is broader.
Compound of 非常 (emergency) + 用 (use, purpose).