Home › Words › G › grumnessgrumnessgrumness means the quality of being grum (morose or sullen).Among words judged in Lexicurio's Arena, grumness ranks #15,430 of 42,785 for Qualifying.EtymologyFrom grum + -ness.nounThe quality of being grum (morose or sullen).Definitions & examples from Wiktionary (CC BY-SA 3.0).