Undulation; irregularities — variations in height or surface, such as bumps or waves in terrain or surfaces.
山道は起伏が多く、歩くのが大変だった。
The mountain path had many undulations and was difficult to walk.
庭の芝生の起伏を整えるために土をならした。
I leveled the soil to even out the undulations in the lawn.
Ups and downs; fluctuations — the highs and lows or variability in emotions, fortune, prices, etc.
株価は最近大きな起伏を見せている。
Stock prices have shown large fluctuations recently.
人生には起伏があるが、それが経験を豊かにする。
Life has its ups and downs, but they enrich our experiences.
彼女の感情は起伏が激しく、注意が必要だ。
Her emotions are volatile, so caution is needed.