reCAPTCHA - technical definition

A method for soliciting help from the general public in order to assist large, text-to-computer projects that digitize thousands of old books. CAPTCHAs are the distorted words found on Web sites that users must type back in to validate that they are humans and not computers. Every day, tens of millions of CAPTCHAs are entered, creating a huge pool of human resources to draw on.

In a reCAPTCHA system, the images of words that the optical character recognition (OCR) scanner cannot decipher are dispersed to several people in the form of a CAPTCHA to get a consensus. For more information or to get reCAPTCHA code, visit www.recaptcha.net. See OCR and CAPTCHA.