passe-partout

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Something, such as a master key, that permits one to pass or go at will.
2. n. A border, such as a mat, that is used to frame or mount a picture.
3. n. An adhesive tape or a gummed paper used for a similar purpose.

Century Dictionary and Cyclopedia

1. n. That by means of which one can pass anywhere; a master-key; a latch-key.
2. n. In engraving, an engraved plate or block forming an ornamental border around an aperture into which the engraved portrait or picture may be inserted;. also, a typographical frame or ornamental border about a page, etc.: a French use.
3. n. 3 A picture-frame consisting usually of a pasteboard back and a piece of glass, between which a drawing or engraving is placed, often with a plain or ornamented mat between it and the glass, the whole being held in position by means of strips of paper pasted over the edges.
4. To place in a passe-partout frame.

Wiktionary

1. n. obsolete That by which one can pass anywhere; a safe-conduct.
2. n. obsolete A master key; a latchkey.
3. n. obsolete A light picture frame or mat of cardboard, wood, etc., usually put between the picture and the glass, and sometimes serving for several pictures.

GNU Webster's 1913

1. n. obsolete That by which one can pass anywhere; a safe-conduct.
2. n. A master key; a latchkey.
3. n. 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.
4. n. A strip of adhesive paper or gummed tape used to mount a picture between a piece of glass and a backing.
5. n. The method of mounting a picture between a piece of glass and a backing, using a passe-partout{4}.

WordNet 3.0

1. n. a mounting for a picture using gummed tape
2. n. key that secures entrance everywhere