Massively single-player is a concept in gaming being popularized by Spore (though it is not new, being seen, among other places, in a somewhat popular web-based game called Kingdom of Loathing.) Essentially, it means that, although the game is single-player and has no direct real-time interaction with other players, the game is massive in terms of available content and interaction, since it regularly checks the online Maxis database for creatures, buildings and any form of content creatable in game, downloading anything that it believes to fit in well with the player's current playing style through the pollinated content system. In a way, this does lend an indirect form of multiplayer to the game through your interactions with other players' creations, especially space-faring cultures in the space stage.