1. (a.) Very swift or quick; fast; as, a rapid stream; a rapid flight\; a rapid motion.

2. (a.) Advancing with haste or speed; speedy in progression; in quick sequence; as, rapid growth; rapid improvement; rapid recurrence; rapid succession.

3. (a.) Quick in execution; as, a rapid penman.

4. (n.) The part of a river where the current moves with great swiftness, but without actual waterfall or cascade; -- usually in the plural; as, the Lachine rapids in the St. Lawrence.

abrupt agile alacritous bluff bold breakneck brisk ceaseless chattering chute constant continual dashing double-quick eagle-winged expeditious express fast fleet flying galloping hair-trigger hasty headlong high-speed hurried hustling immediate impetuous incessant instant instantaneous light of heel light-footed lively machine gun mercurial nimble nimble-footed oscillating perennial perpetual plunging precipitate precipitous prompt pulsating quick quick as lightning quick as thought rapids reckless regular repeated riff riffle ripple running sault sharp sheer shoot snappy spanking speedy staccato steady steep stuttering sudden sustained swift unbroken unceasing unchanging unintermitted unintermittent unintermitting uninterrupted unremitting unstopped unvarying vertical vibrating winged