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[ahy-suh-bahr] /ˈaɪ səˌbɑr/
Meteorology. a line drawn on a weather map or chart that connects points at which the barometric pressure is the same.
Also, isobare
[ahy-suh-bair] /ˈaɪ səˌbɛər/ (Show IPA)
. Physics, Chemistry. one of two or more atoms having equal atomic weights but different atomic numbers.
Compare isotope.
Origin of isobar
1860-65; < Greek isobarḗs “of equal weight,” from ísos iso- + báros “weight” (see bar3)
Related forms
isobarism, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Historical Examples
British Dictionary definitions for isobars


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
(physics) any of two or more atoms that have the same mass number but different atomic numbers: tin-115 and indium-115 are isobars Compare isotope
Derived Forms
isobarism, 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
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Word Origin and History for isobars



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.

Online Etymology Dictionary, © 2010 Douglas Harper
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isobars in Medicine

isobar i·so·bar (ī'sə-bär')

  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.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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isobars in Science
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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