Surprise is the feeling you get when something unexpected happens. When your best friend shows up at your door unannounced, when you open a gift and find something you never imagined, when a test question asks about something you didn't study, you feel surprise. It's that sudden jolt of “I didn't see that coming!”

Surprise can be wonderful or terrible. A surprise party delights the person walking through the door. A pop quiz might fill a classroom with groans. The emotion itself is neutral: it's just your brain rapidly adjusting to new information it wasn't prepared for.

As a verb, to surprise means to cause this feeling in someone else. You might surprise your parents by cleaning your room without being asked. A magician surprises an audience by making a rabbit appear from an empty hat. Military commanders try to surprise their enemies by attacking when and where they're least expected.

The word can also describe the unexpected thing itself: “The biggest surprise of the game was when the losing team scored three goals in the final minutes.” When something catches you completely off guard, you might say you were taken by surprise or caught by surprise.