rigournessEtymologyFrom rigour + -ness; compare Middle English rigornesse, rigournes, rygurnesse.rigourness means synonym of rigour. Lexicurio rates it Rare gem — a strength score of 82 out of 100.nounSynonym of rigour.“In these letters we see [Niccolò] Machiavelli’s political doctrines growing into shape under our eyes, we note his rigourness of method, and also find the greatest eloquence of which he was capable.”