WordWeb Online

1. The quality of being hard to endure, uninviting or formidable
   "the rigourousness of northern winters";
   - asperity, grimness, hardship, rigor [US], rigour [Brit, Cdn], severity, severeness, rigorousness
    
2. Excessive sternness
   "rigourousness of character";
   - severity, severeness, harshness, rigor [US], rigour [Brit, Cdn], rigorousness, inclemency, hardness, stiffness

Type of: difficultness, difficulty, fix [informal], hole [informal], jam [informal], kettle of fish [informal], mess [informal], muddle [informal], pickle [informal], sternness, strictness