/ Dictionary / Index T trim size: Meaning and Definition of Find definitions for: trim' size" Pronunciation: [key] the final size of a product after its unnecessary parts have been cut off or removed: The trim size of the book in 612 inches by 9 inches. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. trim rail trim tab Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language