Definition - What does Volatility mean?
Volatility describes the speed at which a substance vaporizes. It is directly related to the vapor pressure of that substance. At higher pressures, substances will vaporize more readily. Volatility is usually used in reference to liquids; however, it also relates to substances which can go directly from a solid into a vapor.
Safeopedia explains Volatility
Volatility is directly proportional to vapor pressure. Vapor pressure is the pressure during which the gas phase of a substance is in equilibrium with its liquid phase or solid phase (known as the condensed phases). At the liquid's normal boiling point, the atmospheric pressure is the same as the temperature at which its vapor pressure is equal to surrounding pressure in the atmosphere.