• synonyms


  1. an instrument for determining the specific gravity of a liquid, commonly consisting of a graduated tube weighted to float upright in the liquid whose specific gravity is being measured.
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Origin of hydrometer

First recorded in 1665–75; hydro-1 + -meter
Related formshy·dro·met·ric [hahy-druh-me-trik] /ˌhaɪ drəˈmɛ trɪk/, hy·dro·met·ri·cal, adjectivehy·drom·e·try, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for hydrometer

Historical Examples

  • If this hydrometer is placed in a liquid, it will sink to a certain depth.

    The Automobile Storage Battery

    O. A. Witte

  • The rubber tubing on the hydrometer should not be withdrawn from the cell.

  • The first is that the readings taken with a hydrometer will then be misleading.

  • This is another reason why hydrometer readings should be used as a guide.

  • It indicates the strength and is measured by the hydrometer.

British Dictionary definitions for hydrometer


  1. an instrument for measuring the relative density of a liquid, usually consisting of a sealed graduated tube with a weighted bulb on one end, the relative density being indicated by the length of the unsubmerged stem
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Derived Formshydrometric (ˌhaɪdrəʊˈmɛtrɪk) or hydrometrical, adjectivehydrometrically, adverbhydrometry, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for hydrometer


1670s, from hydro- + meter (n.3).

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Online Etymology Dictionary, © 2010 Douglas Harper

hydrometer in Medicine


  1. An instrument used to determine specific gravity, especially a sealed graduated tube, weighted at one end, that sinks in a fluid to a depth indicating the fluid's specific gravity.gravimeter
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Related formshy′dro•metric (hī′drə-mĕtrĭk) adj.hy•drome•try n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

hydrometer in Science


  1. An instrument used to measure the density of a liquid as compared to that of water. Hydrometers consist of a calibrated glass tube ending in a weighted glass sphere that makes the tube stand upright when placed in a liquid. The lower the density of the liquid, the deeper the tube sinks.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.