indelible ink used for marking linen, clothes, etc
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Examples from the Web for marking ink
Historical Examples of marking ink
Because on the other days you forgot to bring home the marking-ink.
I have my own business to attend to in the city without always thinking about marking-ink.