A term that is mostly used by Transmeds & Truescums, which means a non-dysphoric woman larping as nonbinary.
The term is a combination of the pronoun they and the term AFAB, and is commonly used to make fun of & mock women who identify as NB without changing their female appearance, and call out anyone who doesn't use their pronouns.
A: Mary told me she wants to be called Moi, and goes now by they/them.
B: But she is still presenting female and still says she's straight?
A: She's probably a Theyfab, just give her some time.
B: I wouldn't tell her that to her face, she gets pretty mad about it!
Non dysphoric person larping as nonbinary that's transphobic and seni-often even homophobic that has inserted themselves into the lgbt community which they neither appreciate or understand, that is afab
A: Did you know anna came out as a "non-binary"
B:Pfff, shes a trender theyfab