Entry 1 sense Webster, 1913 Pycnometer · Pyc·nom·e·ter · IPA /pɪkˈnɒmɪtə(ɹ)/ 01 n. A specific gravity bottle; a standard flask for measuring and comparing the densities of liquids. 1. A specific gravity bottle; a standard flask for measuring and comparing the densities of liquids.(Physics)