1a(1): harsh inflexibility in opinion, temper, or judgment : SEVERITY
//The least one might observe is that this muddle of moralism and laxity, extreme rigor and casual permissiveness, arduous altruism and nonchalant selfishness, has consequences.
1a(2): the quality of being unyielding or inflexible : STRICTNESS
//Their abandonment of this terminology is part of an effort to soften the rigor of some of the rigid consequences thought to flow from the mechanical application of this dichotomy.
1a(3): severity of life : AUSTERITY
//… a moral rigor and growth that might help this country.
4: strict precision : EXACTNESS
// Tentatively one might suggest that what characterizes science is the rigor of its methodology …