What is Bulldog Edition?

Legal Definition
A bulldog edition is an early edition in the press cycle of a newspaper or other print publication.

For instance, the Sunday New York Times publishes its bulldog edition, about 100,000 copies, for distribution around the country, at about noon on Saturday. Other large metropolitan newspapers in the United States may offer a local Sunday bulldog edition for delivery to subscribers and available at newsstands and in racks on Friday or Saturday.

Although the origin of the term is unclear, the Encyclopedia of Word and Phrase Origins suggests "the term dates back to New York City’s newspaper wars of the 1890s, when rival papers were competing for morning readers with special editions sold by street vendors very early in the day. These papers were baptized 'bulldogs' presumably because the publishers fought like bulldogs over circulation."

In the 1940 film Citizen Kane, Kane tells his wife Susan, “The bulldog's just gone to press,” to which Susan sarcastically replies, "Well, hurray for the bulldog!"
-- Wikipedia
Legal Definition
A periodical edition of something that is not a newspaper usually.