/ Dictionary / Index D dummy joint: Meaning and Definition of Find definitions for: dum'my joint" Pronunciation: [key] a slot cut into a concrete slab to prevent serious fractures. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. dummy block Dumont Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language