What is undetectable HIV mean and can I get HIV having sex with someone who is undetectable?

HIV. Undetectable usually refers to the inability to detect viral RNA by pcr while on treatment for HIV disease. This lowers the risk of transmission to others, but does not eliminate it. So the answer is yes, you can be infected. Go and get tested and do not have unprotected sex with anyone. Hope you are negative and stay that way.