Atrigirl, also known as atringirl atrinagirl, refers to an atrinary girl, this is also abiatrinary.
As the definition of atrinary states, it is referring to any genders that are completely unrelated to maleness, masculinity, femaleness, femininity, neutrois-ness, or neutrality, and is nowhere in between those things, while not necessarily feeling genderless.
One's gendered part is a girl. Someone who is a atrigirl may feel as if they're a girl while not being related to maleness, masculinity, femaleness, femininity, neutrois-ness, or neutrality, and feels as if they're nowhere in between any of them.
This could be due to feeling a connection to girlhood rather than femaleness. A atrigirl may feel as if they're a girl while also not being a part of the gender trinary.
The male counterpart to this gender is atriboy.
History
The term was coined by Reddit user u/hiitsyaz in August 2021, with no exact date.
Atrigirl was coined due to wanting to show how differently one can experience their gender(s), due to how (stereotypically) femininity is associated with being a girl. This isn't the case though, as one can present however one wants to, regardless of their gender.
Flag
The flag was created by an unknown user on or before October 28, 2021.[1] It is a mix of the abiatrinary flag and the girl/female flag.
Etymology
The name of this gender is a combination of "girl" and "atrinary".