mannosePronunciation: /ˈmanəʊz, -s/Definition of mannose noun [mass noun] Chemistry a sugar of the hexose class which occurs as a component of many natural polysaccharides. Chemical formula: C6H12O6 Origin: late 19th century: from mannite 'mannitol' + -ose2mannose in other Oxford dictionaries Definition of mannose in the US English dictionary