- (of rules, standards, etc.) unambiguously clear: This muddies the waters of what should be a brightline rule.
- Physical Chemistry. brightline spectrum.
Origin of brightline
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for bright-line
But monochromatic or "bright-line" light is, by its nature, incapable of being so diffused.
Possibly all such stars have passed through a bright-line stage; but further evidence on the point is needed.