Definition of hydrometer

• n. - An instrument for determining the specific gravities of liquids, and thence the strength spirituous liquors, saline solutions, etc.
• n. - 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.