chalk

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A soft compact calcite, CaCO₃, with varying amounts of silica, quartz, feldspar, or other mineral impurities, generally gray-white or yellow-white and derived chiefly from fossil seashells.
• noun A piece of chalk or chalklike substance in crayon form, used for marking on a blackboard or other surface.
• noun Games A small cube of chalk used in rubbing the tip of a billiard or pool cue to increase its friction with the cue ball.
• noun A mark made with chalk.
• noun Chiefly British A score or tally.
• transitive verb To mark, draw, or write with chalk.
• transitive verb To rub or cover with chalk, as the tip of a billiard cue.
• transitive verb To make pale; whiten.
• transitive verb To treat (soil, for example) with chalk.

from The Century Dictionary.

• noun In geological nomenclature the term chalk has been employed with a variety of meanings. In the English subdivisions of the Cretaceous system the Chalk constitutes the upper part of this system, resting on the Galt and Greensand, which in turn lies on the basal division or Wealden.
• To rub or mark with chalk.
• To manure with chalk.
• Figuratively, to make chalky-white; blanch; make pale.
• To mark; trace out; describe: from the use of chalk in marking lines.
• In Scotland, to mark the door of a burgh tenant with chalk, an old mode of notice to quit, which is still competent.
• noun In geology, a soft white rock, consisting almost entirely of carbonate of lime in a pulverulent or only slightly consolidated state, and readily soiling the fingers when handled.
• noun A piece of prepared chalk used for marking on a dark surface.
• noun A point scored in a game: so called from its being recorded with chalk.
• noun An account. See to chalk up, below.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To rub or mark with chalk.
• transitive verb To manure with chalk, as land.
• transitive verb To make white, as with chalk; to make pale; to bleach.
• transitive verb [Colloq.] to sketch with, or as with, chalk; to outline; to indicate; to plan.
• noun (Min.) A soft, earthy substance, of a white, grayish, or yellowish white color, consisting of calcium carbonate, and having the same composition as common limestone.
• noun (Fine Arts) 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.
• noun a mineral of a bluish color, of a slaty texture, and soiling the fingers when handled; a variety of argillaceous slate.
• noun [Slang] by a long way; by many degrees.
• noun (Fine Arts) a drawing made with crayons. See Crayon.
• noun See Cretaceous formation, under Cretaceous.
• noun a cord rubbed with chalk, used for making straight lines on boards or other material, as a guide in cutting or in arranging work.
• noun a preparation of chalk, cinnamon, and sugar in gum water, much used in diarrheal affection, esp. of infants.
• noun (Geol.) See Cretaceous period, under Cretaceous.
• noun a pit in which chalk is dug.
• noun See Crayon, n., 1.
• noun steatite or soapstone, a soft magnesian mineral.
• noun an indurated clayey ocher containing iron, and used by painters and artificers; reddle.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun uncountable A soft, white, powdery limestone.
• noun countable A piece of chalk, or, more often, processed compressed chalk, that is used for drawing and for writing on a blackboard.
• noun Tailor's chalk.
• noun uncountable, climbing A white powdery substance used to prevent hands slipping from holds when climbing, sometimes but not always limestone-chalk.
• noun US, military, countable A platoon-sized group of airborne soldiers.
• noun US, sports The prediction that there will be no upsets, and the favored competitor will win.
• verb To apply chalk to anything, such as the tip of a billiards cue.
• verb To record something, as on a blackboard, using chalk.
• verb To use powdered chalk to mark the lines on a playing field.
• verb figuratively To record a score or event, as if on a chalkboard.