/ Dictionary / Index J joist: Meaning and Definition of Find definitions for: joist Pronunciation: ( joist), [key] — n. any of a number of small, parallel beams of timber, steel, reinforced concrete, etc., for supporting floors, ceilings, or the like. —v.t. to furnish with or fix on joists. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: joist (Thesaurus) Joinville jojoba Related Content Daily Word Quiz: placid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language