Unless otherwise clearly required by the context, as used in this article:

(a) "Unavailable" means either that a vacancy in office exists and there is no deputy authorized to exercise all of the powers and discharge the duties of the office, or that the lawful incumbent of the office, including any deputy exercising the powers and discharging the duties of an office because of a vacancy and his duly authorized deputy, are absent or unable to exercise the powers and discharge the duties of the office.

(b) "Emergency interim successor" means a person designated pursuant to this article, in the event the officer is unavailable, to exercise the powers and discharge the duties of an office until a successor is appointed or elected and qualified as may be provided by the Constitution, statutes, charters and ordinances or until the lawful incumbent is able to resume the exercise of the powers and discharge the duties of the office.

(c) "Office" includes all state and local offices, the powers and duties of which are defined by the Constitution, statutes, charters, and ordinances, except the office of Governor, and except those in the Legislature and the judiciary.

(d) "Attack" means any attack or series of attacks by an enemy of the United States causing, or which may cause, substantial damages or injury to civilian property or persons in the United States in any manner by sabotage or by the use of bombs, missiles, shellfire, or atomic, radiological, chemical, bacteriological, or biological means or other weapons or processes.

(e) "Political subdivision" includes counties, cities, towns, districts, authorities, and other public corporations and entities, whether organized and existing under charter or general law.