The act of undulating; a waving motion or vibration; as, the undulations of a fluid, of water, or of air; the undulations of sound.
A motion to and fro, up and down, or from side to side, in any fluid or elastic medium, propagated continuously among its particles, but with no translation of the particles themselves in the direction of the propagation of the wave; a wave motion; a vibration.
A (Core) Nia Move in which you undulate, or wave, your spine -- from top to bottom, and then bottom to top.
wave-like motion; a gentle rising and falling in the manner of waves
a wave structure and a wave structure requires a medium