A faux/fake Rugby Shirt. A shirt that looks like a Rugby shirt (or in the style of), but is not made to the specifications of a genuine Rugby Shirt (i.e. No double stitching and a lighter fabric). While a Fugby Shirt looks like a real Rugby Shirt, it would be torn to shreds in an actual Rugby game.
That's a nice Barbarians Rugby Shirt you have. Thanks, but it's a Fugby Shirt with the Barbarian colours.