To shudder means to shake or tremble suddenly, usually from fear, cold, disgust, or some other strong feeling. When you shudder, your body makes an involuntary shaking motion, like a quick wave passing through you.

You might shudder when you step outside on a freezing morning and the cold hits you all at once. You might shudder watching a scary movie at the moment when something frightening appears on screen. Some people shudder at the thought of eating foods they find disgusting, like when someone mentions Brussels sprouts or liver. The shaking happens without you deciding to do it: your body simply reacts.

A shudder is different from regular shaking. It's sudden, brief, and intense, like your whole body is saying “no, thank you” to whatever caused it. A building might shudder during an earthquake. A car engine might shudder when it's having trouble starting.

The word captures that specific moment when something affects you so strongly that your body physically responds. When you read a ghost story that makes you shudder, you're experiencing exactly what the word describes: that quick, involuntary shake that says this moment got to you.