1
: happening in a short amount of time : happening quickly
a rapid [=quick] change in temperature
There's been rapid growth in the number of new businesses in the town.
Scientists are concerned about the rapid disappearance of the island's coral reefs.
2
: having a fast rate
a rapid heartbeat
rapid breathing
3
: moving quickly
She carefully guided the boat through the rapid water.
Cite this Entry
“Rapid.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/rapid. Accessed 15 Apr. 2026.
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