The senior or principal member or head of a staff, or the principal assistant in a staff capacity to a person in a command capacity; the head or controlling member of a staff, for purposes of the coordination of its work; a position that in itself is without inherent power of command by reason of assignment, except that which is invested in such a position by delegation to exercise command in anothers name.
CHIEF OF STAFF
Meaning of CHIEF OF STAFF in English
DOD English dictionary of military terms. Английский словарь военных терминов DOD. 2012