The "captcha" is an obfuscated image with some random letters and numbers, that is placed on a form to ensure, that no robots can submit it.
I've noticed, that:
- during form creation ("Website & Content > Forms > Add") the "security image" term is used
- on user configuration page ("Configuration > Users > General") the "Captcha code" term is used
I have no preference over one or another name, but I just want for same term to be used across In-Portal.