open book noun 4open-book adjective 1forms 1 noun4 •Something whose salient aspects are obvious or easily interpreted.There is one, with a dark and thoughtful eye, Who is to all others a mystery; But his soul is to me an open book, And I read his mood in his slightest look; ... — 1860 •A person who responds candidly to questions or openly displays their emotions or intentions.He is an open book. Everyone can see that he removes nothing, conceals nothing, reserves nothing for himself. — 1986 •An inside angle in the rock. •An open book decomposition. open-book adjective1 •Designating exams in which specified external resources, potentially including textbooks, glossaries, study notes, calculators, etc. may be used. formsopen books
