inch of mercury

noun

a unit of atmospheric pressure, being the pressure equal to that exerted by a column of mercury one inch high under standard conditions of temperature and gravity: 33.864 millibars. Abbreviation: in. Hg

Origin of inch of mercury

First recorded in 1825–35

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018