Definition: The opposite of a detail texture. Like a detail texture, scrottox is a monochrome image drawn using modulate2X blend mode, but where a detail texture is tiled more heavily than the base texture so as to provide fine detail when zoomed in close, a scrottox layer is tiled less heavily in order to provide coarse lumpiness when the view is zoomed out (see screenshots at the end of this page).
Usage: "That terrain texture looks horribly flat if you zoom the camera way out. Let's add a scrottox layer to fix that."
Etymology: MotoGP made heavy use of scrottox layers, but we lacked a good name for them until one of the artists said "the purpose is to make things look dirty, grungy and wrinkled. Like a scrot*m, or a pair of bollocks."