'Photometer' definitions:

Definition of 'photometer'

From: WordNet
noun
Measuring instrument for measuring the luminous intensity of a source by comparing it (visually or photoelectrically) with a standard source
noun
Photographic equipment that measures the intensity of light [syn: light meter, exposure meter, photometer]

Definition of 'Photometer'

From: GCIDE
  • Photometer \Pho*tom"e*ter\, n. [Photo- + -meter: cf. F. photom[`e]tre.] (Physics) An instrument for measuring the intensity of light, or, more especially, for comparing the relative intensities of different lights, or their relative illuminating power. [1913 Webster] Photometric