A story arc (a contraction of "over-arching storyline") is a sequence of series installments,TV episodes, comic issues, or a certain period of time in a Video Game that puts characters through their paces in response to a single impetus; basically, an ongoing storyline. This can be a few episodes, an entire season, or even the focus of the entire series.
What I quoted above from TvTropes pretty much sums up about story arcs in common mediums such as through television, comic books, video games (to a length), etc. Now, does that exact same definition apply to the roleplaying medium, though? I've came to realize how tricky this sort of concept can be when it comes down to a ongoing storyline, and can be pretty hard to describe to others as well. I'm putting this up to civil debate over how story arcs can/should be applied towards a roleplay.