A trilogy refers to a set of three books, movies, or any other form of storytelling media that are connected and tell a single continuous story. Full definition
The iconic purple dragon of video games is hitting our current generation of consoles with his original trilogy of epic adventures. (twinfinite.net)
Also I did lots of shooting near hub areas in trilogy so I don't know what he is talking about. (pcgamesn.com)
It makes sense to push the new and prequel movie characters and locations, since we had so much content from the original trilogy in the last game. (diskingdom.com)