Definition of rapid adjective from the Oxford Advanced Learner's Dictionary

      

    rapid

     adjective
    adjective
    BrE BrE//ˈræpɪd//
     
    ; NAmE NAmE//ˈræpɪd//
     
     
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  1. 1  [usually before noun] happening in a short period of time rapid change/expansion/growth a rapid rise/decline in sales The patient made a rapid recovery.
  2. 2  done or happening very quickly a rapid pulse/heartbeat The guard fired four shots in rapid succession. The disease is spreading at a rapid rate. Which Word?fast / quick / rapidThese adjectives are frequently used with the following nouns: fast car/​train/​bowler/​pace/​lane quick glance/​look/​reply/​decision/​way rapid change/​growth/​increase/​decline/​progress Fast is used especially to describe a person or thing that moves or is able to move at great speed. Quick is more often used to describe something that is done in a short time or without delay. Rapid, swift and speedy are more formal words. Rapid is most commonly used to describe the speed at which something changes. It is not used to describe the speed at which something moves or is done:a rapid train We had a rapid coffee. Swift usually describes something that happens or is done quickly and immediately:a swift decision The government took swift action. Speedy has a similar meaning:a speedy recovery. It is used less often to talk about the speed at which something moves:a speedy car. For the use of fast and quick as adverbs, .
  3. Word Origin mid 17th cent.: from Latin rapidus, from rapere ‘take by force’.
See the Oxford Advanced American Dictionary entry: rapid