Its surprising in such an usually edge-case oriented community that no-one nominated sex, any sport, any physical game (like dodge ball), any drinking game, any get-nude of a game, and such. It seems like everyone automatically agreed -or at least that consensus was quickly reached- that "game" means "something to be played mostly seating in a not-so-big room", or alternatively, something in which the abstracts of the game rules or guidelines can be rated regardless of social or material context (i.e., I would not play forum strip-poker neither online hide-and-seek, while for all the games that were named here and I know, an online version either exists or seems plausible enough).
Disclaimer: I'm not stating that implementability as a forum or online game is the basis to decide weither something is a game or not in this context, and such discussion probably deserves its own thread, if someone is interested.