Frustration is a feeling of annoyance that occurs when something doesn't go as you expect. There are few things more likely to cause frustration for an impatient driver than rush hour traffic.
When you can't get what you want, or you're stuck in some way, you'll experience frustration. A spelling bee competitor who almost wins will feel frustration. The thing that causes you to feel this way can also be called a frustration — like your moody sister, the frustration of your home life. Frustration comes from the Latin frustrationem, "a deception or a disappointment."