Definition of: kinetic theory

Physics
Any theory of the constitution of bodies which explains their properties by the motion of their particles, especially that according to which the elasticity of gases is due to the rapid motion of their molecules, which dart about in straight lines with an average velocity that increases with the temperature, until deflected by encounters with one another or with the walls of the containing vessel. This theory has been found capable of explaining nearly all the phenomena of gases, and is now generally accepted.