If a vehicle or a machine judders, it shakes hard and roughly, in ugly little bursts — you feel it in your bones. The engine judders; the brakes judder; an old bus judders to a stop. It is especially British; American speakers more often say shake, shudder, or vibrate. Though actually, people shudder (a quick shake from cold or fear); cars, planes, and machines judder. The word itself sounds like the thing: a hard, cheap shake, not a smooth vibration. Neutral everyday English, a little informal, very common in talk about cars.