To startle means to suddenly surprise or frighten someone, causing them to jump or react without thinking. When you sneak up behind your friend and they didn't hear you coming, the sound of your voice might startle them into spinning around with wide eyes. A loud noise can startle a sleeping cat into leaping off the couch. A bird might be startled into flight by a passing shadow.

The word captures that brief moment of alarm before your brain figures out what's happening. You're walking peacefully down the hallway when a door slams, and your heart jumps: you've been startled. It's different from scaring someone on purpose to be mean. Being startled is usually quick and harmless, and once the surprise passes, you realize there was nothing to worry about.

The feeling of being startled is involuntary. Your body reacts before your mind catches up. You might gasp, flinch, or freeze for a split second. Animals have this reaction too: it's an ancient survival instinct that helped our ancestors react quickly to danger. These days, you're more likely to be startled by a honking car horn or someone dropping books than by anything truly dangerous.