rapidity

UK: /rəˈpɪdɪti/ US: /rəˈpɪdɪti/ ,(rə pid′i tē)

WordReference Random House Unabridged Dictionary of American English © 2026

ra•pid•i•ty  (rə pid′i tē), n. 

1. a rapid state or quality; quickness;
   celerity.

Also, rap•id•ness  (rap′id nis). 

• Latin rapiditās. See rapid, -ity
• 1610–20

Synonyms

swiftness, fleetness. See speed. 

WordReference Random House Learner's Dictionary of American English © 2026

rap•id /ˈræpɪd/   adj., -er, -est, n. 
adj. 

1. fast, quick-moving, swift:
   rapid motion; rapid growth.

n. 

2. Geography Usually, rapids. [plural] a part of a river where the current runs very swiftly.

ra•pid•i•ty /rəˈpɪdɪti/  rap•id•ness, n. [uncountable]
rap•id•ly, adv. See -rape-.

WordReference Random House Unabridged Dictionary of American English © 2026

rap•id  (rap′id), adj., -er, -est, n. 
adj. 

1. occurring within a short time;
   happening speedily:
   rapid growth.
2. moving or acting with great speed;
   swift:
   a rapid worker.
3. characterized by speed:
   rapid motion.

n. 

4. Geography Usually, rapids. a part of a river where the current runs very swiftly.

• Latin rapidus tearing away, seizing, swift. See rape¹, -id⁴
• 1625–35

rap′id•ly, adv. 
Synonyms

• 2. See quick.