Etymology: (1350–1400; ME rigour < L rigor stiffness =rig(ēre) to be stiff +-or -or1)
Definition of 'rigor'
Princeton's WordNet
1. (noun)asperity, grimness, hardship, rigor, rigour, severity, severeness, rigorousness, rigourousness something hard to endure "the asperity of northern winters"
2. (noun)cogency, validity, rigor, rigour the quality of being valid and rigorous
3. (noun)severity, severeness, harshness, rigor, rigour, rigorousness, rigourousness, inclemency, hardness, stiffness excessive sternness "severity of character"; "the harshness of his punishment was inhuman"; "the rigors of boot camp"
2. (noun)rigor a sense of chilliness, with contraction of the skin; a convulsive shuddering or tremor, as in the chill preceding a fever
3. (noun)rigor the becoming stiff or rigid; the state of being rigid; rigidity; stiffness; hardness
4. (noun)rigor see 1st Rigor, 2
5. (noun)rigor severity of climate or season; inclemency; as, the rigor of the storm; the rigors of winter
6. (noun)rigor stiffness of opinion or temper; rugged sternness; hardness; relentless severity; hard-heartedness; cruelty
7. (noun)rigor exactness without allowance, deviation, or indulgence; strictness; as, the rigor of criticism; to execute a law with rigor; to enforce moral duties with rigor; -- opposed to lenity
Definitions of rigor 
