/ Dictionary / Index B brightline spectrum: Meaning and Definition of Find definitions for: bright'line spec'trum Pronunciation: (brīt'līn"), [key] — Physical Chem. Physical Chem. the spectrum of an incandescent substance appearing on a spectrogram as one or more bright lines against a dark background. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. bright-field brightness Related Content Daily Word Quiz: mamba Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language