A scan through the original script indicates that it's just called "the game" in both the dialogue and the episode direction
PICARD: We also have an opportunity to introduce the game to Starfleet Academy.
and
WESLEY'S POV - THE GAME (OPTICAL)
A view of the bridge -- with the familiar GAME OVERLAY superimposed on top. The playing field has a cone and a disc coasting across it. Picard and Beverly are visible beyond the overlay, looking straight at us.
The Memory Alpha wiki refers to it as the "Ktarian Game" (based on the race of aliens who provided it), something echoed by this mini-documentary on the Startrek.com website.
"[Nothing the crew had ever encountered could have prepared them for] the threat they encountered in the form of the seemingly benign Ktarian Game"
