The Collaborative International Dictionary of English v.0.48:

clipboard \clipboard\ n.
   a small writing board with a clip attached at the top for
   holding papers.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

clipboard
    n 1: a small writing board with a clip at the top for holding
         papers

The Free On-line Dictionary of Computing (30 December 2018):

clipboard

    A temporary memory area, used to transfer
   information within a document being edited or between
   documents or between programs.  The fundamental operations are
   "cut" which moves data from a document to the clipboard,
   "copy" which copies it to the clipboard, and "paste" which
   inserts the clipboard contents into the current document in
   place of the current selection.

   Different Graphical User Interfaces vary in how they handle
   the different types of data which a user might want to
   transfer via the clipboard, some (e.g. the X Window System)
   support only plain text, others (e.g. NEXTSTEP) support
   arbitrarily typed data such as images.

   (1996-08-23)