The Collaborative International Dictionary
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.
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.
WordNet
n. an indelible ink for marking clothes or linens etc.
Usage examples of "marking ink".
Then the customer of comparatively tender years would get suddenly disconcerted at having to deal with a woman, and with rage in his heart would proffer a request for a bottle of marking ink, retail value sixpence (price in Verloc's shop one-and-sixpence), which, once outside, he would drop stealthily into the gutter.
They found a wide selection of photographs of Elia Duphade, cut from newspapers: in every one showing the ornate tribal rings her smallest fingers were encircled in red marking ink.
I knew that it would take ages to get that marking ink off my hand.
Bill Rivenbark would reply, wiping his hands on an apron stained with produce spills and marking ink.