What is Nonbinary?

Nonbinary definition and meaning on Dictionary terms:
not consisting of, indicating, or involving two.
Mathematics. noting or relating to a system of numerical notation that does not have a base of 2: The decimal system is nonbinary.
noting or relating to a person with a gender identity or sexual orientation that does not fit into the male/female or heterosexual/homosexual divisions.
relating to, intended for, or common to any gender; gender-neutral: nonbinary pronouns, first names, and honorifics.