Jus lié is a thickened gravy. It is a brown stock that is thickened with cornflour or arrowroot mixed with a little cold water.
Traditional English style gravy is made using the sediment and juices from roasted meat. Flour is lightly browned in fat heated in the roasting pan. Stock and the meat juices are stirred in and simmered until the sediment lifts off and the liquid thickens. It is strained before serving hot as an accompaniment to the roast meat.