(1):

(a.) Manifesting, exercising, or favoring rigor; allowing no abatement or mitigation; scrupulously accurate; exact; strict; severe; relentless; as, a rigorous officer of justice; a rigorous execution of law; a rigorous definition or demonstration.

(2):

(a.) Severe; intense; inclement; as, a rigorous winter.

(3):

(a.) Violent.