What is a shout line on book covers?

A shout line on a book cover is like a subtitle that tells you a little bit more about the book. For example, Australian author, Trent Jamieson's urban fantasy novel "Managing Death" has the shout line: "Reaping - it's a grim job but someone's got to do it". That gives the reader some idea of what the main character's occupation might be.

Films have shout lines too. "Fair Game" starring Naomi Watts and Sean Penn has: "Wife, Mother, Spy". The family movie "The Incredibles" has: "Superheroes at your service!"