photomask (?f??t???m??sk) n (Printing, Lithography & Bookbinding) an opaque image on a transparent plate that is used to filter light so the image can be transferred, used to etch patterns for integrated circuitsCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014