A pooh-bah is a person who has a lot of power and/or influence. They may hold (but not necessarily fulfill) many offices at the same time, and they are often seen as pompous or self-important.
The word originates from a character in W. S. Gilbert’s The Mikado (1885). In the opera, Pooh-Bah bears the title ‘Lord High Everything Else’; his behaviour matches the definition above.
Hannah McCall 
Back in the 1960s when MAD magazine was my required reading, there was an item which included a scene from the American Revolution, in the background was a poster which had the words ‘Taxation Without Representation is Pooh-Bah’. A fine example of being irreverent while still holding to the basic principal.
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