Literally: rare – astray – Han China – astray
Alternately: Dense jargon. Gibberish. Nonsense. Incomprehensible, unintelligible, incoherent.
Notes: This phrase will usually be written in phonetic kana characters rather than kanji. Even when they are used, the kanji are ateji; that is, they were assigned to the phrase some time after its invention due to their pronunciation rather than their meaning. As such, the pun parts can also be rendered as 糞, “excrement,” or the whole can become 陳奮翰奮, or perhaps other variations.
The phrase apparently comes from Edo-era mockery of the difficult-to-understand, Chinese-laced jargon of Japanese Confucian scholars, much in the way that modern readers might make fun of people who lose themselves in academese.