The frontiers between the three super-states are in some places arbitrary, and in others they fluctuate according to the fortunes of war, but in general they follow geographical lines.
Eastasia, smaller than the others and with a less definite western frontier, comprises China and the countries to the south of it, the Japanese islands and a large but fluctuating portion of Manchuria, Mongolia, and Tibet.
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.