Rapid means something which occurs quickly (fast), As in, "he flipped through the dictionary rapidly" Rapid also refers to a section of a river where the river bed has a relatively steep gradient causing an increase in water flow and turbulence.
This defines a rapid population increase.
A rapid change in density with depth in the ocean is called a thermocline.
A rapid reaction between oxygen and a fuel is called combustion.
A rapid change in temperature with depth in the ocean is called thermocline. A rapid change in density with depth in the ocean is called the pynocline.Thermocline
That is called oscillation.
The 1920s was a decade of rapid industrial growth such growth is called the Roaring Twenties.
Rapid Eye Movement
th a
a cataract
Rapids
fusillade
Stuff.