passe-partout

plural passe-partouts · alternative passepartout

1. That by which one can pass anywhere; a safe-conduct.

   Synonyms: safe-conduct

2. A master key.

   The traditional (or modern) way of confronting complexity was to find a secure point of reference that could serve as foundation, a passe-partout, a master key from which everything else could be derived.

   1998, Paul Cilliers, Complexity and Postmodernism: Understanding Complex Systems, Psychology Press, →ISBN, page 112

   Synonyms: passkey

3. A light picture frame or mat of cardboard, wood, etc., usually put between the picture and the glass, and sometimes serving for several pictures.

   A new introduction for use in conjunction with passe-partout framing is a series of corner pieces which are readily folded round the corners of the finished passe-partout, giving it a certain added effect and slight embellishment.

   1933, William Crookes, T. A. Malone, George Shadbolt, J. Traill Taylor, William Blanchard Bolton, Thomas Bedding, The British Journal of Photography

   Synonyms: mat, matting