weather term
Isobar
A line on a weather map connecting points of equal atmospheric pressure, used to visualise high- and low-pressure systems.
Isobars work like contour lines on a topographic map, but for air pressure instead of elevation. Widely spaced isobars indicate a gentle pressure gradient and light winds, while tightly packed isobars indicate a steep pressure gradient and strong winds, since air moves faster when it's flowing from high to low pressure over a shorter distance.
Read the full article: The Beaufort Wind Scale Explained.