It was a day of lassitude too, hot and close, with, I am told, a rapidly fluctuating barometer.
Men like Schiaparelli watched the red planet—it is odd, by-the-bye, that for countless centuries Mars has been the star of war—but failed to interpret the fluctuating appearances of the markings they mapped so well.
Dense clouds of smoke or dust, visible through a powerful telescope on earth as little grey, fluctuating patches, spread through the clearness of the planet’s atmosphere and obscured its more familiar features.
There are no more uses of "fluctuate" in the book.
Show samples from other sources
Cattle markets tend to fluctuate a lot, and some years, you don’t make much of anything.
Nicholas Sparks -- The Longest Ride
My courage and my resolution is firm; but my hopes fluctuate, and my spirits are often depressed.