Force per unit area.
The pressure that a component of a gaseous mixture would have if it alone occupied the same volume at the same temperature as the mixture.
The derivative of pressure
The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the column of air lying directly above the point in question.
The character and amount of atmospheric pressure change during a specified period of time, often a three-hour period preceding an observation.
The atmospheric pressure at mean sea level, either directly measured or, most commonly, empirically determined from the observed station pressure.