CAPTCHA

noun1

1. •
   (Internet) 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.

   • A CAPTCHA is a quick check to make sure that an actual person, rather than a computer program, is using the website. Web applications use CAPTCHA […] — 2014