The definition of baro means pressure or weight.
An example of the baro prefix is in the word barometer, which is a device that measures atmospheric pressure.
weight or pressure, esp. atmospheric pressure: barograph
Origin of baro-from Classical Greek baros, weight from barys, heavy: see grave
Weight; pressure: barometer.
Origin of baro-From Greek baros weight ; see gwerə-1 in Indo-European roots.