The story
Coined by a team of researchers at Carnegie Mellon University in 2000 as a loose acronym of “completely automated public Turing test to tell computers and humans apart”.
Etymology from Wiktionary, CC BY-SA 4.0.
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Today it means: A computerized test requiring the human user to perform a task deemed to be difficult to automate, such as entering a displayed series of distorted characters or describing images, to demonstrate that they are a human and not a computer program. Full definition →