run in
The tendency of the sections of a book,
particularly the sections at or near the center of
a large book having considerable sewing swell, to
collapse inward, causing the book to lose its
shape, and (generally) to become loose in its
case. Run in is usually caused by excessive swell
in the spine, or by sewing that is too loose.
![[CoOL]](/icons/sm_cool.gif){kind=icon}