The Collaborative International Dictionary of English v.0.48:

markup \markup\ n.
   1. (Commerce) The amount added to the cost to determine the
      asking price.
      [WordNet 1.5]

   2. (printing) Instructions for the typesetter that are
      written on the copy (e.g. underlining words that are to be
      set in italics).
      [WordNet 1.5]

   3. (Legislation) Changes in proposed legislation drafted in
      conference, as contrasted with changes resulting from the
      amendment process.
      [PJC]