You searched for: “undulation
undulation (s) (noun), undulations (pl)
1. In a wave-like motion; a gentle rising and falling in the manner of waves.
2. 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.
3. A regular rising and falling, or movement, to alternating sides.
4. One of a series of wavelike bends, curves, or elevations.