A person who feels that they should be from a different ethnicity, meant in a similar way to transexual.
Generally used by white people to exoticify and assume entitlement of a culture that is not theirs. Kinda racist.
White Girl: Hey look at me being all kawaii and eating sushi, I love Japanese people, I'm totally transethnic because I think I should be Japanese
Non-racist person: Uhm...that's objectifying and wrong, stop it please. Just stop. No.