an open book

: having no enclosing or confining barrier : accessible on all or nearly all sides

: being in a position or adjustment to permit passage : not shut or locked

: having a barrier (such as a door) so adjusted as to allow passage

: to move (something, such as a door) from a closed position

: to make available for entry or passage by turning back (something, such as a barrier) or removing (something, such as a cover or an obstruction)

: to make available for or active in a regular function

: opening

: open and unobstructed space: such as

: open air

: a set of written sheets of skin or paper or tablets of wood or ivory

: a set of written, printed, or blank sheets bound together between a front and back cover

: a long written or printed literary composition

: derived from books (see ¹book 1) and not from practical experience

: shown by ledgers

: to register (something, such as a name) for some future activity or condition (as to engage transportation or reserve lodgings)

: to schedule engagements for

: to set aside time for