convection

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The act or process of conveying; transmission.
2. n. Physics Heat transfer in a gas or liquid by the circulation of currents from one region to another.
3. n. Physics Fluid motion caused by an external force such as gravity.
4. n. Meteorology The transfer of heat or other atmospheric properties by massive motion within the atmosphere, especially by such motion directed upward.

Century Dictionary and Cyclopedia

1. n. The act of carrying or conveying; specifically, the transference of heat or electricity through the change of position of the heated or electrified body: distinguished from conduction (which see). When a portion of a liquid or a gas is heated above the temperature of surrounding portions, it increases in volume, and, thus becoming specifically lighter, rises, while the cooler portions of the fluid rush in from the sides and descend from the upper parts of the vessel. Convection currents are thus produced, and the liquid or gas is soon heated throughout. This principle is used in heating a house by a hot-air furnace. The Gulf Stream is a grand convection current, carrying the heat of the equator toward the pole. (See heat.) Similarly, electricity may be transmitted by convection by the motion of the electrified body itself, as when the electricity of a conductor is discharged by a point, it being carried off by a stream of electrified air-particles.
2. n. by liberation of the latent heat of evaporation which remains with the aqueous vapor contained in the air until it is liberated by condensation into cloud. In so far as the liberated heat remains in the cloud, it may be consumed in reëvaporating the cloudy particles or be lost by radiation; in so far as it is brought down to the earth with the rain or snow, it affects the local climate powerfully.

Wiktionary

1. n. The process of conveying something.
2. n. physics The transmission of heat in a fluid or gas by the circulation of currents.
3. n. meteorology The vertical movement of heat and moisture, especially by updrafts and downdrafts in an unstable air mass. The terms convection and thunderstorm are often used interchangeably, although thunderstorms are only one form of convection. Towering cumulus clouds are visible forms of convection.

GNU Webster's 1913

1. n. The act or process of conveying or transmitting.
2. n. (Physics) A process of transfer or transmission, as of heat or electricity, by means of currents in liquids or gases, resulting from changes of temperature and other causes.

WordNet 3.0

1. n. the transfer of heat through a fluid (liquid or gas) caused by molecular motion
2. n. (meteorology) the vertical movement of heat or other properties by massive motion within the atmosphere