powder keg
noun [ C ] uk/ˈpaʊ.də ˌkeɡ/ us/ˈpaʊ.dɚ ˌkeɡ/
火药桶；一触即发的局势；危险的地方
a situation or a place that could easily become extremely dangerous
The build-up of forces in the region is creating a powder keg. 在该地区加强军备是在制造紧张局势。
The new tax is a political powder keg which could result in widespread violence. 新的税收政策是个政治火药桶，会引起大范围的激烈反应。