The word "undulate" is correct and usable in written English.
You can use it to describe something that moves or fluctuates in a wave-like manner. For example, "The leaves in the wind undulated and danced in the breeze."
In 1934 it was seen to undulate "like the waves of the ocean".
In China the dragon of the New Year was a great paper creation made to undulate by the dancing steps of the bearers underneath.
The most important of these are the Sobaek Mountains, which undulate in a long S-shape across the peninsula.
Crocodiles and aquatic lizards, such as some monitors (family Varanidae) and the marine iguana (Amblyrhynchus cristatus), undulate their bodies and tails from side to side while holding the limbs against the body.
You walk up and down pale wooden floorboards that seem to undulate, like a ship's decking.
See how the stripes in a 19th-century woollen tiger rug from Tibet, for example, have been made to flow and undulate away from its spine.
As he runs light over them, the surfaces bend, the animals undulate.
In one of his aphorisms, he pronounced: "The forms of virtue are erect, the forms of pleasure undulate.
Melodies tend to undulate and often feature a descending inflection; rhythmic characteristics include frequent changes of metre and the use of syncopation.
Melodic contours undulate, sometimes with a descending inflection, and singers achieve rhythmic complexity through special breathing techniques they use to vary durational values.
Most melodies feature stepwise motion and undulate with a descending inflection.
