undulate

undulate \UN-juh-layt; UN-dyuh-\, intransitive:

To move in, or have, waves; to vibrate; to wave; as, undulating air.

The actors' hands quiver and the poles undulate in the wind.
-- Peter Marks, "'The Caucasian Chalk Circle': Brecht Can Be Fun.", New York Times, May 25, 1998

Rather than tuna, several hundred white-sided dolphins come into focus, undulating crisply through the sea surface below.
-- Carl Safina, Song for the Blue Ocean:Encounters Along the World's Coasts and Beneath the Seas

Most startling was the dancer's exposed, undulating abdomen, which she could adroitly activate while hardly moving her feet.
-- Emily Wortis Leider, Becoming Mae West

Undulate derives from Latin undulare, from undula, a little wave, from unda, a wave.