undulate

Short definition from Wiktionary

Verb

1. 1
   To cause to move in a wavelike motion.
2. 2
   To cause to resemble a wave.
3. 3
   To move in wavelike motions.
4. 4
   To appear wavelike.

Adjective

1. 1
   Wavy in appearance or form.
2. 2
   Changing the pitch and volume of one's voice.
3. 3
   sinuous, winding up and down.