An idiom that is closest to meaning: "I have absolutely no idea what it means." It's far more extreme than "I don't understand it."

For me this phrase is not extreme. It simply means that the thing is not understood, as Al 4 says. . As an aside: At a conference in China, one time a Greek guy asked about "It's all Greek to me". He said that he discovered that when English speakers do not understand something they can say "It's all Greek to me". When the Greek, like himself, do not understand something, they can say "It's all Chinese to me.". Being in China, he was told that if Chinese do not understand something, they can say, "It is in the language of the gods". Maybe you can work out the idiom he was told about.

It is an idiom meaning "I don't understand this". I would use it when something is written in English but I don't understand it because it uses too many technical terms. This page has has some translations of the phrase (I don't know if they are correct): http://en.wikipedia.org/wiki/Greek_to_me 看起來像天書。/看起来像天书 聽起來像鳥語。/ 听起来像鸟语 聽起來像火星話。/听起来像火星话

Yes, it's an idiom to say you don't understand it - "it's confusing to me". The Greek alphabet is slightly different to the Roman alphabet, so when faced with a different alphabet, the English speaker's first reaction is to not understand it. ;) That's the basic logic. Some equivalents in other languages: French: C'est chinois. (It's Chinese) Czech: Je to pro mne španĕlská vesnice. (It's a Spanish village to me) And more... here: http://www.omniglot.com/language/idioms/incomprehensible.php (Ouch for the Esperanto phrase!!)

一窍不通 的意思 习惯用法啦。