noun, noun which may take the genitive case particle 'no'
swift current; rapids
Refers to a fast-flowing part of a river, often used in descriptions of nature, geography, or metaphorical rapid change.
この川は急流が多いので、カヌーには向かない。
This river has many rapids, so it's not suitable for canoeing.
急流の音が遠くから聞こえてきた。
The sound of the swift current could be heard from afar.