capt·cha 
(kăpchə) Computers
(kăpchə) Computers n.
A security feature, as on a webpage, that attempts to distinguish between legitimate human users and bots by requiring users to perform a mildly challenging task such as deciphering distorted text.
[Acronym of c(ompletely) a(utomated) p(ublic) T(uring test to tell) c(omputers and) h(umans) a(part), coined in 2000 by the researchers who developed the security feature and intended to suggest a colloquial pronunciation of CAPTURE.]