/ Dictionary / Index L loss function: Meaning and Definition of Find definitions for: loss' func"tion Pronunciation: [key] (in decision theory) a function that expresses the loss incurred when a decision is made in terms of various factors. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. loss loss leader Related Content Daily Word Quiz: modify Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language