A mockbuster is a movie that looks very similar to a popular movie, but was made more quickly and cheaply. It's like a copycat movie, with a similar-looking title, story, and actors. The reason they're called mockbusters is because they're made to look like they're from the same company as the original movie, but they're from a different company. Mockbusters often come out shortly after the original movie, usually straight to DVD or for a digital release.