Pronunciation: (op'tu-miz"um), [key]
1. a disposition or tendency to look on the more favorable side of events or conditions and to expect the most favorable outcome.
2. the belief that good ultimately predominates over evil in the world.
3. the belief that goodness pervades reality.
4. the doctrine that the existing world is the best of all possible worlds.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.