undulation

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.

undignified, undirected, undischarged, undisclosed, undiscovered, undisputed, undistinguished, undisturbed, undivided, undo, undoing, undone, undoubted, undoubtedly, undreamed-of, undress, undressed, undrinkable, undue, undulate, unduly, undying, unearned, unearth, unearthly, unease, uneasily, uneasiness, uneasy, uneatable, uneconomic, uneconomical, uneconomically, unedited, uneducated, unemloyment, unemployed, unemployment, unemployment benefit, unencumbered,