Definitions
1.noun(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.
2.nounA burst of rapid fire.
3.adjectiveVery swift or quick."a rapid stream"
4.adjectiveSteep, changing altitude quickly. (of a slope)
5.adjectiveNeeding only a brief exposure time. (of a lens, plate, film, etc.)
6.adjectiveViolent, severe.
7.adjectiveHappy.
8.adverb(archaic or colloquial) Rapidly.