rapid

Moving, acting, or occurring with great speed. synonym: fast.

An extremely fast-moving part of a river, caused by a steep descent in the riverbed.

In photography, said of plates, lenses, and subjects which require short exposure or print rapidly.

Moving or doing swiftly or with celerity; acting or performing with speed; quick in motion or execution: as, a rapid horse; a rapid worker or speaker.

Swiftly advancing; going on or forward at a fast rate; making quick progress: as, rapid growth; rapid improvement; a rapid conflagration.

Marked by swiftness of motion or action; proceeding or performed with velocity; executed speedily.

Gay.

=Syn. 1–3. Fast, fleet, expeditious, hasty, hurried.

A swift current in a river, where the channel is descending; a part of a river where the current runs with more than its ordinary celerity; a sudden descent of the surface of a stream, more or less broken by obstructions, but without actual cataract or cascade: usually in the plural.

Very swift or quick; moving with celerity; fast