noun, noun which may take the genitive case particle 'no', adverb
as soon as possible; ASAP; with the utmost urgency
Stronger than 至急; used in business or formal requests to demand immediate action. Often used adverbially with に or as a noun with の.
大至急ご返信ください。
Please reply as soon as possible.
これは大至急の案件です。
This is a matter of the utmost urgency.
大至急に処理いたします。
We will handle it with the utmost urgency.