GNU Collaborative International Dictionary of English

Found one definition

1.       
   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]