high alert; severe warning
Used in official or news contexts to describe a state of heightened vigilance or a strong cautionary notice.
With the typhoon approaching, the meteorological agency is calling for high alert.
The police placed themselves on high alert against the possibility of terrorism.
Compound of 厳重 (strict, severe) and 警戒 (vigilance, caution). The exact historical derivation is uncertain, but the word follows standard Sino-Japanese compounding patterns.