ZombiU will allow you to paint symbols on the environment, leaving messages for other players.
The messages are only visible on the Game Pad in room-scanning mode, Polygon reports.
It's up to the player how they combine the symbols to point out elements like threats or secrets - or perhaps even play mischievous pranks and ruin somebody else's good times. Oh you kids.
It's not yet clear how Ubisoft will determine which messages show up in your game, but it sounds similar to From Software's efforts with Demon's and Dark Souls, so presumably a solution is at hand. This kind of thing is called "asynchronous multiplayer" and it's neat-o, amirite?
Zombi U is expected when the Wii U launches on some mysterious, magical day we're not yet allowed to know anything about.