NOUN (2)

1. the amount added to the cost to determine the asking price;

2. detailed stylistic instructions for typesetting something that is to be printed; manual markup is usually written on the copy (e.g. underlining words that are to be set in italics);

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]

WordNet (r) 3.0 (2006):

markup
    n 1: the amount added to the cost to determine the asking price
    2: detailed stylistic instructions for typesetting something
       that is to be printed; manual markup is usually written on
       the copy (e.g. underlining words that are to be set in
       italics)

The Free On-line Dictionary of Computing (30 December 2018):

markup

    In computerised document preparation, a method of adding
   information to the text to indicate the logical components of a
   document, instructions for layout of the text on the page or other
   information which can be interpreted by some automatic system.

   For example, HTML (Hypertext Markup Language) adds tags to the
   text to indicate the appearance and behaviour it should have when
   displayed by a web browser.  E.g.:

    This is bold text.

    This is a link to FOLDOC.

   Other examples of markup languages are troff, SGML (on which
   HTML was based) and XML.

   (2012-12-14)