Hero Defense

This is similar to a mixture of tower defense and MOBA but doesn't fit either. For one this does not fit tower defense because there's no towers or equivalent by default. For another this does not fit MOBA by not having constant presence of enemy heroes who are doing the exact same thing as you, and there's no enemy core/nexus/whatever to destroy. This is infact closer to horde mode.

So far the game type is seen mostly in game mods rather than as commercial products.