Isobar

A line drawn on a weather map to connect places that have the same atmospheric pressure. Since winds tend to blow almost parallel to isobars, the direction and speed of storms can be predicted accurately by using isobaric charts.

I"so*bar (?), n. [Iso- + Gr. &?; weight.] (Phys. Geog.)

A line connecting or marking places upon the surface of the earth where height of the barometer reduced to sea level is the same either at a given time, or for a certain period (mean height), as for a year; an isopiestic line. [Written also isobare.]

© Webster 1913