the.com/undulation
A wave that forgot to stop being a verb.
means A smooth, rhythmic rising-and-falling motion or wave-like form, whether in water, sound, hills, or a dancer's spine.
from From Latin unda, meaning wave — the same root that washes through inundate and abundant, all overflowing with the same liquid energy.
PhysicsLight and sound both travel as undulations.
LandscapeRolling hills are described as undulating terrain.
MusicVibrato is a controlled undulation of pitch.