Undulate

To have a wavy border or form.

Also, to rise and fall like a wave.

For example, the border of a wound may undulate, as may the edge of a rash.

And sound waves may undulate.

The word 'undulate' comes from the Latin 'undula' which is the diminutive of 'unda' meaning wave.

So 'undula' is a little wave.

The adjective is 'undulant.' Undulant fever, also called brucellosis, is an infectious disease characterized by a rising and falling (undulant) fever.

It is caused by a bacterium called Brucella that can be transmitted in unpasteurized milk or cheese of cattle, sheep, and goats or by contact with diseased animals.