天书

1. a book from heaven—abstruse or illegible writing

♦ 对我来说, 这本书就跟~一样难懂。 To me this book is as difficult as a book from heaven. or This book is all Greek to me.

♦ 这封信字迹太潦草, 像~似的。 This letter is as illegible as hieroglyphics.

2. imperial edict (in ancient China)