1. any culture medium that uses agar as the gelling agent • Syn: nutrient agar • Hypernyms: culture medium, medium • Hyponyms: blood agar • Substance Meronyms: agar-agar 2. a colloidal extract of algae; used especially in culture media and as a gelling agent in foods • Syn: agar-agar • Hypernyms: gum • Substance Holonyms: nutrient agar