Your favorite word could be our Word of the Day!
in physics, a discontinuous spectrum consisting of bright lines resulting from radiation from an incandescent vapor or gas;
If the gas is made incandescent by heat or an electric discharge, the resulting spectrum is a bright-line, or emission, spectrum, consisting of a series of bright lines against a dark background.
Single out; focus on; emphasize: My final comment, and I want to bright-line it
[1980s+; fr the use of a usu yellow felt pen to mark important passages]