an open book
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an open book
1. Something that is easy to understand or decipher. These legal contracts are anything but an open book. Don't worry, this recipe is an open book, even if you're not an experienced baker. Modernist poems have so many allusions to other works that they're not exactly an open book
2. One who acts (or purports to act) honestly, with no secrets. Ask me anything, I'm an open book. Adam says he's an open book, but I've seen him sneaking out of his house late at night. If he says he's an open book, then he's lying—I know he works for the mob!
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.
(like an) open book
Fig. [of someone or something] easy to understand. Jane's an open book. I always know what she is going to do next. The committee's intentions are an open book. They want to save money.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
Something or someone that can be readily examined or understood, as in His entire life is an open book. This metaphoric expression is often expanded to read someone like an open book, meaning "to discern someone's thoughts or feelings"; variations of this metaphor were used by Shakespeare: "Read o'er the volume of young Paris' face," ( Romeo and Juliet, 1:3) and "O, like a book of sport thou'lt read me o'er" ( Troilus and Cressida, 4:5). [Mid-1800s] For an antonym, see closed book.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
an open book
If a person's life or character is an open book, nothing about it is kept secret. `Their lives are an open book,' says a spokesman. `They are good people and she has always been a good kid.' His life is an open book. You know which girl he's dating, which car he's driving. Compare with a closed book.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
an ˌopen ˈbooka person whose behaviour, attitudes, thoughts, etc. are very easy to understand, either because you know them very well or because they are very open and honest: After living with her for 20 years, she’s an open book to me. ♢ His life is an open book. He has no secrets. OPPOSITE: a closed book (to somebody)
Farlex Partner Idioms Dictionary © Farlex 2017