rigor

UK: /ˈrɪgə^r/ US: /ˈrɪgɚ/ ,(rig′ər)

WordReference Random House Learner's Dictionary of American English © 2025

rig•or /ˈrɪgɚ/   n. 

1. [uncountable] the quality of being strict;
   strictness;
   inflexibility.
2. hardship of some kind, as weather or climate:
   [countable] the rigors of winter.
3. careful accuracy:
   [uncountable] the rigor of mathematics.
4. Physiology [uncountable] a rigid condition of the body's muscles when unnaturally stiffened.

Also,[esp. Brit.,] ˈrig•our. 

WordReference Random House Unabridged Dictionary of American English © 2025

rig•or  (rig′ər), n. 

1. strictness, severity, or harshness, as in dealing with people.
2. the full or extreme severity of laws, rules, etc.
3. severity of living conditions;
   hardship;
   austerity:
   the rigor of wartime existence.
4. a severe or harsh act, circumstance, etc.
5. scrupulous or inflexible accuracy or adherence:
   the logical rigor of mathematics.
6. severity of weather or climate or an instance of this:
   the rigors of winter.
7. Pathology a sudden coldness, as that preceding certain fevers;
   chill.
8. Physiology a state of rigidity in muscle tissues during which they are unable to respond to stimuli due to the coagulation of muscle protein.
9. [Obs.] stiffness or rigidity.

Also,[esp. Brit.,] rigour. 

• Latin rigor stiffness, equivalent. to rig(ēre) to be stiff + -or -or¹
• Middle English rigour 1350–1400

Synonyms

• 1. inflexibility, stringency.
• 4. cruelty.

Collins Concise English Dictionary © HarperCollins Publishers::

rigor / ˈraɪɡɔː ˈrɪɡə/ noun

1. a sudden feeling of chilliness, often accompanied by shivering: it sometimes precedes a fever
2. / ˈrɪɡə/ rigidity of a muscle; muscular cramp
3. a state of rigidity assumed by some animals in reaction to sudden shock

Etymology: see rigour

WordReference Random House Unabridged Dictionary of American English © 2025

rig•our  (rig′ər), n. [Chiefly Brit.]

1. British Terms rigor.

Collins Concise English Dictionary © HarperCollins Publishers::

rigour, rigor / ˈrɪɡə/ noun

1. harsh but just treatment or action
2. a severe or cruel circumstance; hardship: the rigours of famine
3. strictness, harshness, or severity of character
4. strictness in judgment or conduct; rigorism

Etymology: 14th Century: from Latin rigor