noun an instrument for determining the specific gravities of liquids, and thence the strength spirituous liquors, saline solutions, ·etc.
2. hydrometer ·noun an instrument, variously constructed, used for measuring the velocity or discharge of water, as in rivers, from reservoirs, ·etc., and called by various specific names according to its construction or use, as tachometer, rheometer, hydrometer, pendulum, ·etc.; a current gauge.