Definition of stock footage (or stock/library shot)

previously-shot footage or film of common elements or scenes, such as canyons or deserts in the American West, or travelogue shots (e.g., skylines, airplane takeoffs/landings, famous places, etc.) that are kept in a film archive or library and used to fill in portions of a movie in different film productions, thereby saving the time of reshooting similar scenes over and over; a stock shot refers to an unimaginative or commonplace shot that looks like it could be stock footage