n. Any one of various rocks, of eruptive origin, in general older than the Tertiary, crystalline-granular in texture, and of a dark-greenish color.n. A very hard and close-textured stone used for putting the last edge on lancets and other delicate surgical instruments, etc.n. A name in New Zealand for several varieties of jade, specifically for pounamu or nephrite, found chiefly on the west coast of the Middle Island: formerly much used by the Maoris for weapons, implements, and ornaments.