undulation/ˌʌndjuˈleɪʃn; ?@ -dʒu-; ˌʌndʒə`leʃən/ n(a) [U] wave-like movement or appearance 波动; 起伏.(b) [C] one of a number of wave-like curves or slopes 波状的弯曲或斜坡 The downs fell in gentle undulations to the sea. 这块丘陵地略带倾斜伸向大海.
牛津英汉双解词典