Proper noun
(fandom slang) The universe in which the television series Doctor Who, Torchwood, and The Sarah Jane Adventures, as well as related books, comics and other stories, are set.
(possibly dated) The totality of all things connected to the series Doctor Who, including the fictional universe which is its setting, the real-world sets in which it is filmed, its actors and fandom, etc.
Source: en.wiktionary.org