The Collaborative International Dictionary of English v.0.48:

Ideogram \I*de"o*gram\, n. [Ideo- + -gram; cf. F. id['e]ograme.]
   1. An original, pictorial element of writing; a kind of
      hieroglyph expressing no sound, but only an idea.
      [1913 Webster]

            Ideograms may be defined to be pictures intended to
            represent either things or thoughts.  --I. Taylor
                                                  (The
                                                  Alphabet).
      [1913 Webster]

            You might even have a history without language
            written or spoken, by means of ideograms and
            gesture.                              --J. Peile.
      [1913 Webster]

   2. A symbol used for convenience, or for abbreviation; as, 1,
      2, 3, +, -, ?, $, ?, etc.
      [1913 Webster]

   3. A phonetic symbol; a letter.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ideogram
    n 1: a graphic character that indicates the meaning of a thing
         without indicating the sounds used to say it; "Chinese
         characters are ideograms" [syn: ideogram, ideograph]

The Free On-line Dictionary of Computing (19 January 2023):

ideogram

    A symbol representing a concept.  Nearly all
   ideograms are pictograms - pictures of the thing represented,
   others are merely conventional.  An example of non-pictorial
   ideogram might be the degree symbol (a superfix circle) when
   used for temperature.

   (2014-07-30)