convection

(obsolete) The process of conveying something.

(physics) The transmission of heat in a fluid by the circulation of currents.

(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.