/ Dictionary / Index L lumen: Meaning and Definition of Find definitions for: lu•men Pronunciation: (l'mun), [key] — pl. -mens, -mi•na the unit of luminous flux, equal to the luminous flux emitted in a unit solid angle by a point source of one candle intensity. Abbr.: lm the canal, duct, or cavity of a tubular organ. (of a cell) the cavity that the cell walls enclose. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: lumen (Thesaurus) lumbricoid lumen-hour Related Content Daily Word Quiz: menagerie Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language