A meeting is the planned gathering of a group of people for a specific reason. You might attend a meeting for Trekkies who are all fans of "Star Trek," or you may decide to stay home and watch "Star Trek" reruns instead. Wise move.
Meetings are arranged beforehand, and when you show up at one, there will be other people there for the same purpose. Your meeting might be your monthly book group or a quick huddle after work to plan your boss's surprise birthday party. Meeting can also mean "an encounter," like the chance meeting you have with your kindergarten teacher at the grocery store, or "the place things come together," like the meeting of two streams in your yard.