1 ) Juices exuded by roasted meat or poultry.

2 ) A sauce made from these juices by boiling with stock or wine or other liquids (some use vegetable).

3 ) seasoned, and usually thickened with a starch.

There are numerous ways to make gravy, therefore ingredients vary. Terminology can differ regards the term gravy and sauce.
                                                                                                   Some thoughts : "Gravy" or "sauce"?