'Pot liquor' is the liquid left in a covered roasting pan or pot, after cooking. A good example is a pot roast of beef- the roast is cooked with vegetables, spices, and either water or beef stock (stock is much better). The roast is cooked for several hours. The resultant 'pot liquor ' is the remaining liquid- essentially reduced, or wonderfully strong flavored beef stock! It may be used as a thin gravy over the vegetables, the meat or anything you would use gravy on. It may also be thickened, but then it IS gravy.