Shock is a specific condition with a number of different causes. However the rest, when used in the general parlance are subjective descriptions of the severity of a person's condition, and they generally don't have a specific definition. For some, it describes the severity of the diagnosis (eg how bad the injuries are or how far along a disease has progressed), for others, it may mean prognosis (how likely a person is to recover). This information is for the press, and can vary. The American Hospital Association has some guidelines, but they are very general.
Most hospitals will also have some internal documentation on what to tell the press and what it means.
Some of the terms you list can also be used in in-house (that is, within a hospital) assessments, or part of a formal assessment system. For instance, the Injury Severity Score uses these terms as an assessment tool. Some hospitals may also use labels like this among the staff to determine resource allocation to nursing floors. Those vary from place to place.