/ Dictionary / Index L line spectrum: Meaning and Definition of Find definitions for: line' spec"trum Pronunciation: [key] — Physics. Physics. an electromagnetic spectrum consisting of discrete lines, usually characteristic of excited atoms or molecules. Cf. band spectrum, continuous spectrum, spectral line. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. line space line squall Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language