✨📕 The NEWThe NEW Collegiate Dictionary, 12th Edition Over 5,000 words added — Buy Now! Collegiate DictionaryBuy Now!

reaction time

noun

: the time elapsing between the beginning of the application of a stimulus and the beginning of an organism's reaction to it

Browse Nearby Words

Cite this Entry

“Reaction time.” Merriam-Webster.com Medical Dictionary, Merriam-Webster, https://www.merriam-webster.com/medical/reaction%20time. Accessed 29 Nov. 2025.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!