Pastured or Pasture-Raised indicates the animal was raised on a pasture and that it ate grasses and food found in a pasture, rather than being fattened on grain in a feedlot or barn.
Pasturing livestock and poultry is a traditional farming technique that allows animals to be raised in a humane, ecologically sustainable manner. This is basically the same as grass-fed, though the term pasture-raised indicates more clearly that the animal was raised outdoors on pasture.