Nut Job. Yours is the most common question for a new member, so welcome.
There is a movement here to stop using the acronym, and I am participating by trying to use other words or spell it out.
It is confusing, and I hope others will stop using it for the benefit of our new members and clarity of writing. But it does describe in 2 letters the vast mutual experience of us Dads with our soon to be and ex-wives, so there is nothing wrong with it per se.
Volenti non fit injuria