From AMS Glossary
A class of analytical or numerical time-dependent models in which at least two different subsystems of earth's climate system are allowed to interact.
These subsystems may include the atmosphere, hydrosphere, cryosphere, and biosphere. This term is most commonly used for models of the evolution and interaction of earth's atmosphere and ocean. Coupled (two way) interaction between different subsystems can be contrasted with the class of models where the evolution of a subsystem A is affected by the present state of the subsystem B, but changes in A do not have feedback on the evolution of B itself.