n. Any instrument of the form of a fork with three prongs; specifically, a three-pronged fish-spear.n. A spear with three prongs, usually barb-pointed, forming a characteristic attribute of Poseidon (Neptune), the sea-god. See also cut under Poseidon.n. Hence, marine sovereignty; rule over the ocean or sea.n. In Roman antiquity, a three-pronged spear used by the retiarius in gladiatorial combats.n. In geometry, a crunodal plane cubic curve having the line at infinity for one of the tangents at the node, It was discovered and named by Descartes.