An ongoing game is a game that is still in progress.
Mafiascum.net has a very hard-line stance with regards to ongoing games: Discussion of them in any way, shape, or form is illegal. The spirit of the rule is obvious - as Mafia is a game where perception and opinion are paramount, any discussion with someone who's not involved will taint things and can alter the game's outcome. An egregious example would be a player who makes a discussion thread on the topic of "I'm in a game right now, what should I do in this situation?"; a much weaker but still disallowed example would be saying "I'm in another game with X and he's acting the same way there". The latter example highlights how the blanket ban of such discussion can be an obstacle for players who wish to elaborate on meta reads and such, but there is no way to draw an objective line between allowable and banned ongoing game discussion.