The lowest possible temperature, at which point the atoms of a substance transmit no thermal energy - they are completely at rest.
It is 0 degrees on the Kelvin scale, which translates to -273.15 degrees Celsius (or -459.67 degrees Fahrenheit).
(cryogenics) the lowest temperature theoretically attainable (at which the kinetic energy of atoms and molecules is minimal); 0 Kelvin or -273.15 Centigrade or -459.67 Fahrenheit