Source : Webster's Revised Unabridged Dictionary (1913)

Umber \Um"ber\, n. [F. ombre ocherous ore of iron, terre
   d'ombre, It. terra d'ombra, literally, earth of shadow or
   shade, L. umbra shadow, shade. Cf. {Umber}, 3 & 4,
   {Umbrage}.]
   1. (Paint.) A brown or reddish pigment used in both oil and
      water colors, obtained from certain natural clays
      variously colored by the oxides of iron and manganese. It
      is commonly heated or burned before being used, and is
      then called {burnt umber}; when not heated, it is called
      {raw umber}. See {Burnt umber}, below.

   2. An umbrere. [Obs.]

   3. [F. ombre, umbre, L. umbra.] (Zo["o]l.) See {Grayling}, 1.

   4. [Cf. NL. scopus umbretta, F. ombrette; probably fr. L.
      umbra shade, in allusion to its dark brown color. See
      {Umber} a pigment.] (Zo["o]l.) An African wading bird
      ({Scopus umbretta}) allied to the storks and herons. It is
      dull dusky brown, and has a large occipital crest. Called
      also {umbrette}, {umbre}, and {umber bird}.

   {Burnt umber} (Paint.), a pigment made by burning raw umber,
      which is changed by this process from an olive brown to a
      bright reddish brown.

   {Cologne}, or {German}, {umber}, a brown pigment obtained
      from lignite. See {Cologne earth}.

Source : WordNet®

burnt umber
     n 1: dark brown pigment obtained by heating umber
     2: a medium to dark brown color [syn: {chocolate}, {coffee}, {deep
        brown}, {umber}]