Is 'gravy'a proper noun or a common noun?

The noun gravy is a common noun, a Word for any gravy of any kind.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Gravy Lane, Bradford, ME or Gravy Lane, Whitewater, MO
• Gravy Master (seasoning)
• "Gravy Wars: South Philly Foods, Feuds & Attytudes" by Lorraine Ranalli
• "The Gravy Train", 1974 movie with Stacey Keach, Margot Kidder