The phrase "unannounced game" refers to a video game that has not been officially revealed or announced to the public. It is a game project that is being developed secretly without any information shared about it. Full definition
There are two right now that I want to hear more about, though I am really eager to hear about more unannounced games at E3. (playstationlifestyle.net)
Make sure to look out for even more previously unannounced games and release dates at PAX West this weekend. (indiehangover.com)
As part of the process, the union has published a list of projects that members are no longer allowed to work on, and it includes several unannounced games. (warpzoned.com)