To both physician and layman, a chill represents a serious and alarming sign. A combination of both subjective and objective bodily changes, varying in intensity from a tremulous feeling or a sensation of cold to a violent, widespread shivering or rigor, a chill may involve part of the body or its entirety and may be due to external or internal causes (e. g., exposure to cold or bacterial invasion).
With the realization that no clearcut separation can therefore be made, the word "chill" will be applied to the combination of a subjective perception of inward trembling or actual cold and a more or less generalized involuntary muscle tremor visible as an objective sign. Such a definition, first given by Richet1 almost fifty years ago, does not include the lesser degrees of transitory shivering, chilliness or sensations of cold, which may all be due to similar causes and mechanisms, but
PERERA GA. CLINICAL AND PHYSIOLOGIC CHARACTERISTICS OF CHILL. Arch Intern Med (Chic). 1941;68(2):241-260. doi:10.1001/archinte.1941.00200080063005