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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.
1860-65; < Greek isobarḗs of equal weight. See iso-, baro-
Related forms
isobarism, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for isobars
  • Isotherms are lines connecting areas of the same temperature, and isobars connect regions of the same atmospheric pressure.
  • On weather maps, locations of equal pressure are connected by isobars, typically drawn as white lines.
  • The forecasted wind vectors there go across the isobars at a much larger angle than they should.
  • Below is an animation of infrared imagery of the storm, with isobars and the track of the surface low superimposed.
  • They are similar to isobars and isotherms on weather maps.
  • They then connect places that have the same pressure with lines called isobars.
  • isobars, isotherms, etc all are examples of isopleths.
  • The results are presented as the oxygen isobars superimposed on the phase diagram.
  • They have used departures from normal pressure rather than charts of monthly isobars-Ed.
  • Phase diagrams, isotherms, and isobars based on those models can be calculated and drawn for the user's convenience.
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
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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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Encyclopedia Article for isobars


line on a weather map of constant barometric pressure drawn on a given reference surface. The isobaric pattern on a constant-height surface is extremely useful in weather forecasting because of the close association between pressure and weather. Regions of low pressure at sea level tend to be areas of bad weather, especially in winter. At higher elevations the wind blows approximately parallel to the isobars, with low pressure to the left in the Northern Hemisphere and to the right in the Southern Hemisphere with respect to the direction of air movement; the closer together the isobars are, the stronger is the wind speed. Only sea-level pressure patterns are routinely used in meteorology. At higher elevations pressure itself is used to define the reference surface upon which contours of the height above sea level are drawn; dynamically, the height contours of a constant pressure surface are completely analogous to the isobars of a constant-height surface

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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