To frustrate means to prevent someone from accomplishing what they're trying to do, or to make them feel annoyed and defeated when things don't work out. When you're trying to build something and the pieces won't fit together properly, that experience frustrates you. When a goalkeeper blocks shot after shot, she frustrates the other team's attempts to score.

The feeling of frustration is that particular mix of annoyance and disappointment that comes when you keep trying but can't make progress. You might feel frustrated when you're solving a difficult puzzle, when your little brother interrupts your homework for the tenth time, or when you practice a song on the piano but can't get one section right, no matter how many times you try.

Frustration often builds gradually. The first time something doesn't work, you might stay calm. By the fifth or sixth attempt, you feel that rising sense of frustration, sometimes wanting to give up entirely. People often say that learning to handle frustration without giving up is a valuable skill, because many things worth accomplishing will frustrate you at some point along the way.