fluctuate

Something that fluctuates varies or changes — it's the opposite of steady. Like the ups and downs of the stock market or the relationship status of a Hollywood starlet.

Fluctuate is a verb that describes movement, sometimes irregular, but often rising and falling in a wave-like pattern. The tides fluctuate according to the weather and season, for example. Your emotions fluctuate depending on what happens throughout the day, and so does your weight. In fact, you usually weigh less in the morning, before you've eaten. You're also taller, since your spine compresses as you walk around. So your height fluctuates, too.