2. (Slang, based on 1) Adverb (or adjective?) meaning unfashionable: Disco music is out (of fashion).
3. (Slang, based on 1 and closeted: Taking somebody out of the closet) Intransitive verb: The act of letting it be known that a person is lesbian, gay or bisexual. The practice of outing closeted people without their consent has been widely debated in the [LGB community]?.
4. (Slang, based on 3) The act of revealing other secrets about somebody to the public or a third party: He outed her as a smoker. His outing her came as a big surprise to her parents.