a device for showing the operating condition of some system
a signal for attracting attention
(chemistry) a substance that changes color to indicate the presence of some ion or substance; can be used to indicate the completion of a chemical reaction or (in medicine) to test for a particular reaction
obvious to the eye or mind; "a tower conspicuous at a great distance"; "wore conspicuous neckties"; "made herself conspicuous by her exhibitionistic preening"