Source : Webster's Revised Unabridged Dictionary (1913)

Tympan \Tym"pan\, n. [F., fr. tympanum a kettledrum, a panel of
   a door. See {Tympanum}, and cf. {Tymp}.]
   1. A drum. [Obs.]

   2. (Arch.) A panel; a tympanum.

   3. (Print.) A frame covered with parchment or cloth, on which
      the blank sheets are put, in order to be laid on the form
      to be impressed.

   {Tympan sheet} (Print.), a sheet of paper of the same size as
      that to be printed, pasted on the tympan, and serving as a
      guide in laying the sheets evenly for printing. --W.
      Savage.