a form ofcrystalline limestone in which the original crystals have dissolved slowly, usu under the influence of heat and pressure, and recrystallized to form a hard rock with a veined or mottled appearance that can be polished to a very smooth finish

a small glass little ball made of a hard substance, e.g. glass, and used in various children's games

(in pl, but treated as sing.) any of several games played with marbles, the object of which is to hit a mark or hole, to hit another player's marble, or to knock as many marbles as possible out of a ring

informal (in pl) elements of common sense, esp sanity

He seems to have lost his marbles

persons who are born without all their marbles — Arthur Miller