a passkey or master key
a mat used in mounting pictures
a picture mounting in which glass, picture, backing, and often a mat are bound
together, as by strips of gummed paper along the edges
the gummed paper used for such a mounting
Webster’s New World College Dictionary, 4th Edition. Copyright © 2010 by
Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'passe-partout'Fr, lit., passes everywhere