alginic acidPronunciation: /alˈdʒɪnɪk/Definition of alginic acid noun [mass noun] Chemistry an insoluble gelatinous carbohydrate found (chiefly as salts) in many brown seaweeds. The sodium salt is used as a thickener in foods and many other materials. Origin: late 19th century: alginic from alga + -in1 + -icalginic acid in other Oxford dictionaries Definition of alginic acid in the US English dictionary