Source : Webster's Revised Unabridged Dictionary (1913)

Pith \Pith\, n. [AS. pi?a; akin to D. pit pith, kernel, LG.
   peddik. Cf. {Pit} a kernel.]
   1. (Bot.) The soft spongy substance in the center of the
      stems of many plants and trees, especially those of the
      dicotyledonous or exogenous classes. It consists of
      cellular tissue.

   2.
      (a) (Zo["o]l.) The spongy interior substance of a feather.
      (b) (Anat.) The spinal cord; the marrow.

   3. Hence: The which contains the strength of life; the vital
      or essential part; concentrated force; vigor; strength;
      importance; as, the speech lacked pith.

            Enterprises of great pith and moment. --Shak.

   {Pith paper}. Same as {Rice paper}, under {Rice}.