Sorry, probably not very standard terminology. I somehow picked it up from the OReilly book: Fonts & Encodings: From Advanced Typography to Unicode and Everything in Between

Page 55:

""" there are characters with no glyphs. glyphs that can correspond to a number of different characters according to context. Glyphs that correspond to multiple characters at the same time (with weightings assigned to each), and even more possibilities.

The problem of glyphs and characters is so complex that it has gone beyond the realm of computer specialists and has come to be of interest even to philosophers. For example, the Japanese philosopher Shigeki Moro, who has worked with ideographic characters in Buddhist documents, goes so far in his article Surface or Essence: Beyond Character Model Set [274] as to say that Unicode's approach is Aristotelian essentialist and to recommend supplanting it by an approach inspired by Jacques Derrida's theory of writing [114, 115]. The reader interested in the philosophical aspects of the issue is invited to consult [165,156], in addition to the works cited above. """

I think "essentialist" is probably a good description of the philosophy of how Unicode defines characters as opposed to fonts and glyphs, so I adopted it.