"Cross platform" means that something, like software or a game, can work on different types of devices or operating systems, such as computers, smartphones, or consoles. Full definition
We've produced many cross platform games previously, including plenty of mobile titles so we're in prime position to deliver on our promise. (kickstarter.com)
We haven't yet implemented the platform specific features just yet but love the idea of cross platform play and save files. (thisgengaming.com)