passe-partout, ‖Passe partout (päsˌ pärˌto͞oˈ), n. [F., from passer to pass + partout everywhere.]
1. That by which one can pass anywhere; a safe-conduct. [Obs.] Dryden.
[1913 Webster]
2. A master key; a latchkey. [wns=1]
[1913 Webster]
3. A light picture frame or mat of cardboard, wood, or the like, usually put between the picture and the glass, and sometimes serving for several pictures.
[1913 Webster]
4. A strip of adhesive paper or gummed tape used to mount a picture between a piece of glass and a backing. [wns=2]
[WordNet 1.5]
5. The method of mounting a picture between a piece of glass and a backing, using a passe-partout4.
[PJC]