The Collaborative International Dictionary of English v.0.48:

Marking \Mark"ing\, n.
   The act of one who, or that which, marks; the mark or marks
   made; arrangement or disposition of marks or coloring; as,
   the marking of a bird's plumage.
   [1913 Webster]

   Marking ink, indelible ink, because used in marking linen.


   Marking nut (Bot.), the nut of the Semecarpus Anacardium,
      an East Indian tree. The shell of the nut yields a
      blackish resinous juice used for marking cotton cloth, and
      an oil prepared from it is used for rheumatism.
      [1913 Webster]

WordNet (r) 3.0 (2006):

marking ink
    n 1: an indelible ink for marking clothes or linens etc.