Ri·gor n.
1. Rigidity; stiffness.
2. ed. A sense of chilliness, with contraction of the skin; a convulsive shuddering or tremor, as in the chill preceding a fever.
Rigor caloris Physiol., a form of rigor mortis induced by heat, as when the muscle of a mammal is heated to about 50° C. -- Rigor mortis , death stiffening; the rigidity of the muscles that occurs at death and lasts till decomposition sets in. It is due to the formation of myosin by the coagulation of the contents of the individual muscle fibers.