The Collaborative International Dictionary
bully pulpit \bul"ly pul"pit\, n. An exceptionally advantageous position from which to extol one's ideas; -- applied especially to the presidency of the United States, which was described thus by President Theodore Rossevelt.
Douglas Harper's Etymology Dictionary
1904, coined by U.S. president Teddy Roosevelt, in reference to the White House.
Wiktionary
n. (context US English) an advantageous position from which to express one's views
WordNet
n. a public office of sufficiently high rank that it provides the holder with an opportunity to speak out and be listened to on any matter; "the American presidency is a bully pulpit"
Wikipedia
A bully pulpit is a conspicuous position that provides an opportunity to speak out and be listened to.
This term was coined by President Theodore Roosevelt, who referred to the White House as a "bully pulpit", by which he meant a terrific platform from which to advocate an agenda. Roosevelt used the word bully as an adjective meaning "superb" or "wonderful", a more common usage in his time than it is today. Another expression which survives from this era is "bully for you", synonymous with "good for you".
Usage examples of "bully pulpit".
James Robert, champion of merchanters against station governments, would use his bully pulpit with other merchanters.
One of the cowboys stepped into a bully pulpit and lifted a bullhorn to his mouth.
Throughout the 1980s, Ozal privatized state companies, liberalized banking, allowed for free and floating exchange rates, and used the bully pulpit to champion the small-time entrepreneur.