Plain English Meaning
A unit used to measure how heavy the air is pressing down. Higher numbers mean higher pressure; lower numbers mean lower pressure, which often signals weather changes.
Full Definition
A unit of atmospheric pressure equal to one one-thousandth of a bar, or 100 pascals. Standard sea-level atmospheric pressure is 1013.2 millibars, equivalent to 29.92 inches of mercury. Millibars are commonly used in weather reporting and aviation meteorology to express barometric pressure.
Context Anchor
Seen in aviation weather reports, weather charts, and discussions of atmospheric pressure.
Derivation
From the Latin 'mille' (thousand) and 'bar' (from the Greek 'baros' meaning ). A is one-thousandth of a bar, the original metric unit of pressure. Knowing the 'baros' (weight) helps connect millibars to and barometric pressure -- all describing the weight of the .