vapor pressure

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The pressure exerted by a vapor in equilibrium with its solid or liquid phase. At the vapor pressure, there is no net evaporation.
• noun The pressure exerted by water vapor in the atmosphere.

from The Century Dictionary.

• noun See pressure.

from the GNU version of the Collaborative International Dictionary of English.

• (Physics) The pressure or tension of a confined body of vapor of a chemical substance in equilibrium with the solid or liquid form of the substance. The pressure of a given saturated vapor is a function of the temperature only, and may be measured by introducing a small quantity of the substance into a barometer and noting the depression of the column of mercury.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics The pressure that a vapor exerts, or the partial pressure if it is mixed with other gases.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the pressure exerted by a vapor; often understood to mean saturated vapor pressure (the vapor pressure of a vapor in contact with its liquid form)