Rapid

Latin rapidus

Full definition of rapid

Very swift or quick.
a rapid stream; rapid growth; rapid improvement

John Milton (1608-1674)Ascend my chariot; guide the rapid wheels.
1922, Ben Travers, A Cuckoo in the Nest Chapter 5, The most rapid and most seductive transition in all human nature is that which attends the palliation of a ravenous appetite. There is something humiliating about it....Can those harmless but refined fellow-diners be the selfish cads whose gluttony and personal appearance so raised your contemptuous wrath on your arrival?
2013-06-21, Chico Harlan, Japan pockets the subsidy …, Across Japan, technology companies and private investors are racing to install devices that until recently they had little interest in: solar panels. Massive solar parks are popping up as part of a rapid build-up that one developer likened to an "explosion."

(plural rapids)

(often in the plural) a rough section of a river or stream which is difficult to navigate due to the swift and turbulent motion of the water.