The minimum temperature at which a liquid gives off vapor in sufficient concentration to form a mixture with air near the surface of the liquid that will ignite when exposed to an external flame. A flash point is defined to minimize risk during normal storage and handling of the material in question. Any liquid having a flash point below 100 °F is classified as flammable.
Gasoline has a flash point of -40 degrees C (which is also -40 F).
Compiled from several definitions on the 'net.