Genderf*ck, also known as Genderpunk is a term for culture and resistance against gendernormativity. It is an identity that based on a resistance against gender norms, homophobia and transphobia, oppression and societal status. One's actual gender has nothing to do with being genderpunk. One does not have to be trans to be genderpunk.
The main idea of being genderpunk is no caring about the gender binary and challenging the expectations of society. This doesn't mean that genderpunks don't respect other people's gender identity, but they do what ever they want with their own gender and don't care what culture/society thinks "a girl should look like" or "how boy should act".
Examples of genderpunk might include cisgender men who likes traditionally effeminate things. Cis woman who enjoys short hair and dressing butch. Non-binary people who present a 'clashing' way, or in a way to challenging the expectation of people to fit the gender binary. As long as one agrees with the mindset, no matter how they identify, they can be a part of the genderpunk/genderf*ck movement.