"rigorousness" in the noun sense
1. asperity, grimness, hardship, rigor, rigour, severity, severeness, rigorousness, rigourousness
something hard to endure
"the asperity of northern winters"
2. severity, severeness, harshness, rigor, rigour, rigorousness, rigourousness, inclemency, hardness, stiffness
"severity of character"
"the harshness of his punishment was inhuman"
"the rigors of boot camp"
Source: WordNet® (An amazing lexical database of English)
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