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Definition of captcha

captcha

/ˈkæp.tʃə/
cap · tcha
Plural:captchas
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captcha Lexical Profile

captcha Game Scores & Validity

• noun

1

A type of challenge-response security test used on websites to determine whether the user is a human or an automated computer program, typically requiring the user to type distorted letters or select specific objects in a grid of images.

Example

"Before submitting the registration form, she had to solve a captcha by clicking on every square that contained a traffic light."

• Nearby Words

captain
captaincy
captainship
captcha
caption
captioning
captionless

Word Origin & Etymology

Coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper, and John Langford at Carnegie Mellon University as a contrived acronym for 'Completely Automated Public Turing test to tell Computers and Humans Apart', punning on the word 'capture'.

Usage Trend

Historical frequency of usage in published text.

180019102020
Data source: Google Books Ngram Viewer

Cite this Entry

Wordmom. (2026). Definition of Captcha. In Wordmom Dictionary. Retrieved Nov 5, 2026, from https://wordmom.com/dictionary/captcha
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