the final size of a product after its unnecessary parts have been cut off or removed: The trim size of the book in 6½ inches by 9 inches.
Origin of trim size
First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
the size of a book or a page of a book after all excess material has been trimmed off
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