[passe-par.tout] n [F, fr. passe partout pass everywhere] (1675) 1: master key
2. a: [5]mat b: a method of framing in which a picture, a mat, a glass, and a back (as of cardboard) are held together by strips of paper or cloth pasted over the edges
3: a strong paper gummed on one side and used esp. for mounting pictures