overmatter en · NOUN
Etymology
From over- + matter.
Meanings
-
(uncountable) Typeset material that proves to be surplus to requirements.
Casting off is estimating the number of words in a manuscript. Copy fitting is assessing how much space text will take up in a printed document. Both are important in ensuring that you do not end up with pages of overmatter.
2005, Alan Pipe, Production for Graphic Designers, page 48: