Gotcha

CAPTCHA: a program with the unerring ability to make letters and numbers unrecognizable to the human eye. On the other hand, its thwarting of internet bots is debatable.

If the legend of Sisyphus were updated, instead of futilely rolling a stone, the task of the victim would be to submit successfully a single CAPTCHA.

Definition from The Librarian's Weird Hoard (2012- )