be all Greek to someone
be all Greek to someoneBRITISH, AMERICAN or
be Greek to someoneAMERICAN
If you say that something is all Greek to you, you mean that you do not understand it at all. I've no idea what it means — it's all Greek to me. I don't understand legal jargon — it's all Greek to me. Note: The idea behind this expression is that Greek is very difficult to learn and understand, especially because it uses a different alphabet from most other European languages.