It's a discourteous and lazy way of dumping a romantic interest.
Language isn't fixed, the meaning of words, especially "new" words (and ghosting is a new verb) changes over time. That was the original meaning, but it's now applied to all relationships.
>Ghosting is by no means limited to long-term romantic relationships. Informal dating relationships, friendships, even work relationships may end with a form of ghosting.
For clarity, I didn't mean that ghosting was only to do with dumping partners. I suppose I was suggesting that that's the canonical example.