Synonyms for Rapid:

adj.

active (adjective)
lively, running.
fast (adjective)
fast, breakneck, presto, snappy, expeditious, allegro, fleet, hurrying, quick, nimble, swift, galloping, like mad, rushing, hasty, dashing, light-footed, speedy.
hasty (adjective)
darting, feverish, breathless, galloping, rushing, fleet, hurried, breakneck, hasty, bustling, flying, running, swift, quick, impatient, urgent, fast, speedy, pelting, brisk, abrupt, dashing.
very fast (adjective)
swift.
very quick (adjective)
agile, active, brisk, lively, spry, hurried, nimble, breakneck, speedy, fleet, expeditious, mercurial, prompt, swift, hasty, flying, winged, light-footed, ready, fast.

adv.

quickly (adverb)
frenetic, quickly.

adv

quickly (adverb)
quickly, like a shot, like mad, frenetic, in a flash/like a flash/quick as a flash.

n.

hell-for-leather. brief, short. swift (noun)
quick, speedy, hurried, fast, swift.

Other synonyms:

hell-for-leather. active. short. brief. nimble
agile.
Other relevant words:
frenetic, winged, active, agile, lively, quickly, prompt, hell-for-leather, mercurial, ready, spry, listless, brief, short.

Usage examples for rapid

  1. A few rapid steps and she had gained the corner. – The New Tenant by E. Phillips Oppenheim
  2. I had already been fortunate enough to win the countenance of the duke, and from that day my rise was rapid – Calderon The Courtier A Tale by Edward Bulwer-Lytton
  3. Oh, but it is good, going over to it with her quick, rapid habit of movement. – The Heath Hover Mystery by Bertram Mitford