Voted "Other". For me "Campaigning" is defined by a feeling of continuity. This may be because the story is on-going over several adventures, or maybe because the two campaign arcs, even though using different systems, players and game worlds have a sort of conceptual link between each other (for instance, Eternal Companions types of dual games). Players may change but the overall set-up of the adventures and arcs keep on going with different players and characters, and so on and so forth. Even the DMs may change over the years, if the campaign is a homebrew run by a particular association and to become a DM there, you ought to run the signature homebrew of the association. I've seen this before.
So as far as I'm concerned "Campaign" means "continuity", whatever this may particularly mean in each Campaign instance. Campaigns that are linked by some type of continuity may themselves be part of an Uber-campaign of sort.