Trigender

Trigender is a gender identity under the multigender and transgender umbrella terms. Trigender people experience exactly three genders, either simultaneously or moving between the three (the latter one being under the genderfluid umbrella too). These three genders can be any gender, either binary or nonbinary.

History
Trigender was mentioned as one of many valid nonbinary identities in the 2013 text Sexuality and Gender for Mental Health Professionals: A Practical Guide.