Agar-agar

Webster's Dictionary of the English Language

·noun A fucus or seaweed much used in the East for soups and jellies; Ceylon moss (Gracilaria lichenoides).

II. Agar-agar ·add. ·noun A gelatinlike substance, or a solution of it, prepared from certain seaweeds containing gelose, and used in the artificial cultivation of bacteria;

— often called agar, by abbreviation.