n. [ Spectrum + photometer. ] 1. (Opt.) An instrument for measuring or comparing the intensities of the colors of the spectrum. [ 1913 Webster ]

2. (Chem., Physics) An analytical instrument for measuring the degree of absorption of light at different wavelengths by a chemical substance. A specific pattern of absorption intensities at a series of wavelengths is a characteristic of each different chemical substance. [ PJC ]