undulate
verb [ I ] uk/ˈʌn.djʊ.leɪt/ us/ˈʌn.djʊ.leɪt/
波动，起伏;（声音）忽高忽低的;（音量）忽大忽小的;（节奏）忽快忽慢的
to have a continuous up and down shape or movement, like waves on the sea
The road undulates for five miles before a steep climb. 这条路高低起伏了五英里，然后是一个陡峭的爬坡。
the undulating countryside 地势高低起伏的乡村