Define isobar. isobar synonyms, isobar pronunciation, isobar translation, English dictionary definition of isobar. n. 1. A line on a weather map connecting points of equal atmospheric pressure. Also called isopiestic . 2. Any of two or more kinds of atom
Isobar, 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.