The quality of being like soup, especially in terms of being liquid or having a thick, wet texture.
Soupiness is usually a good thing because it means something is like soup, which is often comforting and tasty.
Examples:
The soupiness of the stew made it perfect for a cold day.
I like the soupiness of this porridge.
The soupiness of the mud made it hard to walk through.
The soupiness of the pudding made it slide off the plate.
The soupiness of the rain made everything wet and slippery.
The soupiness of the sauce made it easy to pour over the pasta.