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1. Something hard to endure
   - asperity, grimness, hardship, rigor [US], severity, severeness, rigorousness, rigourousness [Brit, non-standard]
    
2. The quality of being valid and rigorous
   - cogency, validity, rigor [US]
    
3. Excessive sternness
   "the rigours of boot camp"
   - severity, severeness, harshness, rigor [US], rigorousness, rigourousness [Brit, non-standard], inclemency, hardness, stiffness

Sounds like: rigger, rigor

Derived forms: rigours

Type of: believability, credibility, credibleness, difficultness, difficulty, sternness, strictness

Encyclopedia: Rigour