swell; undulation; meander; surge (of a trend, emotion, etc.)

💡 Nuance & Usage: Often used for natural phenomena like large waves or landforms, and also for abstract concepts such as a surge in public opinion, emotions, or market trends. It implies a large, gradual, and often powerful movement or change. (自然現象の大きな波や土地の起伏、また世論や感情、市場の動向など、抽象的な事柄の大きな変動や勢いを表す際に使われます。)