Lines drawn through positions having the same barometric pressure, when reduced to sea level.

Lines of constant pressure. On surface meteorological charts, these contours are used to delineate areas of low and high pressure.

The lines on a weather map that indicate areas of equal air pressure. Tightly packed isobars indicate unsettled weather.

Lines on a weather map that join places of equal atmospheric air pressures. They often look like whirl pools which tell us where there are low and high air pressure areas.

line on a map passing through all points having the same atmospheric pressure

lines on a weather map used to connect points of equal air pressure