rhamnosePronunciation: /ˈramnəʊz, -s/Definition of rhamnose noun [mass noun] Chemistry a sugar of the hexose class which occurs widely in plants, especially in berries of the common buckthorn. Origin: late 19th century: from modern Latin Rhamnus (genus name) + -ose2rhamnose in other Oxford dictionaries Definition of rhamnose in the US English dictionary