(~s, undulating, ~d)
Something that ~s has gentle curves or slopes, or moves gently and slowly up and down or from side to side in an attractive manner. (LITERARY)
As we travel south, the countryside begins to ~ as the rolling hills sweep down to the riverbanks...
His body slowly ~d in time to the music.
VERB: V, V, also V n
undulating
...gently undulating hills.
ADJ