I go with the "one party" definition. Over the last 12 years I've run 4 campaigns (and will start a 5th soon) in one campaign world. Each time the campaign lasted until either the goals of the group were essentially all met, or I got too burned out to continue. Or the rules system changed (we started a new party for 3.0).
All were in the same Campaign World, but in different places or different time periods,or both. They shared timeline, and overall history of the world, religions, etc... but there was no crossover of characters (though some characters from the 1st two campaigns are rulers of a kingdom PCs in later campaigns visited/lived in).
Most of these campaigns had a core of players that were the same, with some changes (about 1/2 the people are the same from beginning to end). But each was still a separate campaign, because the characters, their goals, the story arcs and the adventures were all unique.