Isobar

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.

The quality or state of being equal in weight, especially in atmospheric pressure. Also, the theory, method, or application of isobaric science.

(meteorology)an isogram connecting points having equal barometric pressure at a given time