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See more synonyms for isobar on Thesaurus.com
  1. Meteorology. a line drawn on a weather map or chart that connects points at which the barometric pressure is the same.
  2. Also i·so·bare [ahy-suh-bair] /ˈaɪ səˌbɛər/. Physics, Chemistry. one of two or more atoms having equal atomic weights but different atomic numbers.
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Compare isotope.

Origin of isobar

1860–65; < Greek isobarḗs “of equal weight,” from ísos iso- + báros “weight” (see bar3)
Related formsi·so·bar·ism, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words


Examples from the Web for isobar

Historical Examples

  • In most cases the 29.80-inch isobar furnishes a good limit, out to which the isobars may be traced.

    Practical Exercises in Elementary Meteorology

    Robert DeCourcy Ward

British Dictionary definitions for isobar


  1. a line on a map connecting places of equal atmospheric pressure, usually reduced to sea level for purposes of comparison, at a given time or period
  2. physics any of two or more atoms that have the same mass number but different atomic numberstin-115 and indium-115 are isobars Compare isotope
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Derived Formsisobarism, noun

Word Origin

C19: from Greek isobarēs of equal weight, from iso- + baros weight
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 isobar


1864, coined from Greek isos "equal" (see iso-) + baros "weight," from barys "heavy" (see grave (adj.)). Line connecting places with the same barometric pressure at the same time.

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Online Etymology Dictionary, © 2010 Douglas Harper

isobar in Medicine


  1. Any of two or more kinds of atoms having the same atomic mass but different atomic numbers.
  2. A line on a weather map connecting points of equal atmospheric pressure.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

isobar in Science


  1. A line drawn on a weather map connecting places having the same atmospheric pressure. The distance between isobars indicates the barometric gradient (the degree of change in atmospheric pressure) across the region shown on the map. When the lines are close together, a strong pressure gradient is indicated, creating conditions for strong winds. When the lines are far apart, a weak pressure gradient is indicated and calm weather is forecast.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.