from "NB", which stands for non-binary. These people do not identify with the male or female genders, and usually prefer "they" as a pronoun. They are neither men nor women, and should not be regarded as such.
Enbies can be genderqueer, agender, pangender, or any gender identity that is not binary.
"Chris is an enby, which means they're neither a man nor a woman."
"This is my enbyfriend, TJ."