Origin of millrun
coming directly from a mill, especially without having been sorted: mill-run carpets.
Origin of mill-run
An Americanism dating back to 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
mainly US (of commodities) taken straight from the production line; unsorted as to quality
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