Transtrender, a portmanteau of the words transgender and trend, is a derogatory term used to describe someone who is pretending to be transgender for attention or for pity. Which is a small portion of the nondysphoric community. Oftentimes, this term is used to describe someone who is transgender and does not experience gender dysphoria, which does not make them cisgender, as dysphoria is not needed to be transgender; see gender incongruence.
This term can also be used in a derogatory sense against nonbinary people. Some binary trans folk believe that to be trans, you must be binary. Or for gender non-conforming trans people of any gender, where as some transmedicalists believe you must follow strict expectations of what it means to be male or female. Which draws back into whether someone has Gender Dysphoria, or not. This is because majority people believe if you are a trans man, and have gender dysphoria, doing anything even remotely feminine will trigger that dysphoria, which is not always true.
Another way that this word is used, is to disrespect thoes who identify as tucutes. A Tucute is a trans person, with gender dysphoria or otherwise, who believes you do not need dysphoria to be transgender. The oposite to this term is Truscum. Some nicer alternatives for the two terms is Trans-medic and Trans-med.
This word is mostly used as an insulting adjective.