isallobar A line on a weather chart connecting points of equal change of atmospheric pressure within a specified time period commonly used on synoptic surface charts to depict three-hourly local pressure tendencies. Found on http://www.wordinfo.info/words/index/info/view_unit/2795/
A line on a weather map drawn through points where similar changes in barometric pressure have occurred in a given period of time. Isallobars show regions of rising and falling pressure.
Found on https://www.encyclo.co.uk/local/20784