To fluster means to make someone nervous, confused, or agitated, often by rushing them or catching them off guard. When you're flustered, your thoughts get jumbled and you might forget what you were about to say or do. A student might get flustered during a presentation if someone asks an unexpected question, suddenly losing their train of thought even though they knew the material perfectly a moment before.

You can fluster yourself, too. Realizing you're running late for school might fluster you so much that you forget your lunch on the counter or put on mismatched socks. The word suggests a temporary state of being rattled or thrown off balance, not a deep worry or fear.

People who stay calm under pressure are hard to fluster. A practiced musician won't get flustered if they drop their sheet music right before performing because they've learned to handle unexpected problems smoothly. Teachers know that surprise fire drills sometimes fluster younger students, who may need a moment to collect themselves before lining up properly.

The word can be a noun, too: being in a fluster means being in that confused, scattered state of mind where everything feels harder than it should be.