The belief that one needs to have gender identity disorder/gender dysphoria to be
transgender.
Also the belief that one has to meet
society's expectations of appearance and behaviour of their preferred
gender in order to be considered transgender.
Truscum people usually don't think that transgenderism/transsexualism (two terms that they consider to be strongly attached to one another) is normal human behaviour,but rather applies to a small minority of people who have an innate or acquired psychiatric disorder. They also typically think of anyone who claims they'
re trans without meeting those criteria as a "transtrender", ie. someone who claims to be trans for the sake of being seen as "different", "special" or "a rebel".