gunneraPronunciation: /ˈgʌn(ə)rə, gʌˈnɪərə/Definition of gunnera noun a South American plant with extremely large leaves that resemble rhubarb and which is grown as a waterside ornamental. Genus Gunnera, family Gunneraceae: several species, in particular G. manicata and G. tinctoria Origin:modern Latin, named after Johann E. Gunnerus (1718–73), Norwegian botanistgunnera in other Oxford dictionaries Definition of gunnera in the US English dictionary