How do you spell Undulating

Available Definitions:
1)  a. - Rising and falling like waves; resembling wave form or motion; undulatory; rolling; wavy; as, an undulating medium; undulating ground.
2)  v. t. - To cause to move backward and forward, or up and down, in undulations or waves; to cause to vibrate.
3)  v. i. - To move in, or have, undulations or waves; to vibrate; to wave; as, undulating air.