Is that some officer who holds office in administration of Government departments ?

Can all officers holding office in administration department of PIA/WAPDA/SSGCL/NHA be considered as bureaucrats ?

If not, officers of which Government are considered as bureaucrat ?

All the Government officials are Bureaucrats by definition of the term !

AoA, According to Dictionary.com a bureaucrat is
"an official who works by fixed routine without exercising intelligent judgment."

However German sociologist Max Weber defined a bureaucratic official as the following:-
He is personally free and appointed to his position on the basis of conduct.
He exercises the authority delegated to him in accordance with impersonal rules, and his loyalty is enlisted on behalf of the faithful execution of his official duties.
His appointment and job placement are dependent upon his technical qualifications.
His administrative work is a full-time occupation.
His work is rewarded by a regular salary and prospects of advancement in a lifetime career.
He must exercise his judgment and his skills, but his duty is to place these at the service of a higher authority. Ultimately he is responsible only for the impartial execution of assigned tasks and must sacrifice his personal judgment if it runs counter to his official duties.
Bureaucratic control is the use of rules, regulations, and formal authority to guide performance. It includes such things as budgets, statistical reports, and performance appraisals to regulate behavior and results.

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Khuda Rakhay Salamat lazzat e Zauq e Tajassus ko,
Milay Manzil to katra ker guzar jaon ga Manzil say..

Though all above explanations are valid to elaborate Bureaucrat , yet in practice people from civil services like( CSS , PMS ) are known as civil Bureaucracy/Bureaucrat and people from armed forces are known as military Bureaucracy/Bureaucrat.

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''Surely with every hardship there is relief'' (The Holy Quran 94:6)