Its nonsensical!
Surely its "Going out with...."
So you have Dating ( going on dates, maybe sleeping together but not exclusive), then Going Out With (not living together,but not seeing other people and developing/developed feelings), then Relationship (for me this is more than 6 months but less than 2 years because...) then Long Term Relationship (whether living together/married or not).
Its a bloody stupid word. To me it would mean, if I had to define it, people who have been in a LTR but have to stay in their current arrangement for practical reasons, such a cant afford to run two homes or their house wont sell or similar. The first few times I read it, I assumed that that was what it meant and had to Google it.
Probably going to be told IABU but it really bugs me!