Source : Webster's Revised Unabridged Dictionary (1913)

Monogram \Mon"o*gram\, n. [L. monogramma; Gr. ? single + ?
   letter, fr. ? to write: cf. F. monogramme. See {Graphic}.]
   1. A character or cipher composed of two or more letters
      interwoven or combined so as to represent a name, or a
      part of it (usually the initials). Monograms are often
      used on seals, ornamental pins, rings, buttons, and by
      painters, engravers, etc., to distinguish their works.
      Monogram.

   Note: The monogram above, combining the letters of the name
         {Karolvs}, was used by Charlemagne.

   2. A picture in lines; a sketch. [R.]

   3. An arbitrary sign for a word. [R.]

Source : WordNet®

monogram
     n : a graphic symbol consisting of 2 or more letters combined
         (usually your initials); printed on stationery or
         embroidered on clothing