isobar i·so·bar (ī'sə-bär')
Any of two or more kinds of atoms having the same atomic mass but different atomic numbers.
A line on a weather map connecting points of equal atmospheric pressure.
A line drawn on a weather map connecting places having the same atmospheric pressure. The distance between isobars indicates the barometric gradient (the degree of change in atmospheric pressure) across the region shown on the map. When the lines are close together, a strong pressure gradient is indicated, creating conditions for strong winds. When the lines are far apart, a weak pressure gradient is indicated and calm weather is forecast.