Coverage in filmmaking (not to be confused with Script Coverage), means that you've shot a given scene in all possible ways appropriate for that particular scene, over and above a Master Shot.   Said another way, it's the combined total of individual shots (from a variety of different angles) to be inter-cut with the “Master Shot.”  A director might ask his cinematographer or editor, "Do you think we got enough coverage for that scene."  

The video included with this definition provides a great overview of coverage, including tips on knowing when you've got it.