n. One of the heroes who, according to the ancient Hellenic myth, sailed with Jason in the ship Argo to Colchis on the Euxine sea in quest of the golden fleece.n. plural Those who emigrated to California about the time of the discovery of gold there: as, the Argonauts of '49.n. [lowercase] A cephalopod mollusk, known also as the paper-nautilus and paper-sailor.