n. A stiff paperboard or pasteboard used as book covers
the GNU version of the Collaborative International Dictionary of English
n. A kind of stout pasteboard.
The Century Dictionary and Cyclopedia
n. A stout kind of pasteboard especially used by binders for the stiff boards upon which the leather or other material for bindings is pasted or glued.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. stout pasteboard used to bind books
Word Usage
"OR: Trace the pattern onto cardstock, and then glue that to millboard, which is the thick non corrugated cardboard that they make book covers and the backs of sketchbooks etc from or onto masonite."