rapid

(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.

A burst of rapid fire.

Very swift or quick.

"a rapid stream"

Steep, changing altitude quickly. (of a slope)

Needing only a brief exposure time. (of a lens, plate, film, etc.)

Violent, severe.

(archaic or colloquial) Rapidly.