Genderqueer is a term for people who “queer” their gender in some way. Genderqueer people fall outside cisgender norms, i.e., through being non-binary, gender non-conforming, or transgender. It is especially used in the specifically non-binary sense, referencing gender identity which is neither male nor female, is a combination of the two binary genders, or is on a continuum between those two genders (among other non-binary experiences). Genderqueer can therefore refer to someone who doesn’t follow binary gender norms.
Other definitions/things to note:
Genderqueer has also been used as a gender modality for a person who subverts gender or expectations related to gender, regardless of assigned gender. Some, but not all, Genderqueer people identify as transgender.