What is a shaking, shivering, or shuddering, as in the cold fit which precedes a fever; in old medical writings, a chill of less severity than a rigor, and more marked than an algor called?

horror — A shaking, shivering, or shuddering, as in the cold fit which precedes a fever; in old medical writings, a chill of less severity than a rigor, and more marked than an algor. (Webster's 1913.)