a soft, earthy substance, of a white, grayish, or yellowish white color, consisting of calcium carbonate, and having the same composition as common limestone.-finely prepared chalk, used as a drawing implement; also, by extension, a compound, as of clay and black lead, or the like, used in the same manner. see crayon.-to rub or mark with chalk.-to manure with chalk, as land.-to make white, as with chalk; to make pale; to bleach.