The Collaborative International Dictionary of English v.0.48:

Chalk \Chalk\ (ch[add]k), n. [AS. cealc lime, from L. calx
   limestone. See Calz, and Cawk.]
   1. (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.
      [1913 Webster]

   2. (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.
      [1913 Webster]

   Black chalk, a mineral of a bluish color, of a slaty
      texture, and soiling the fingers when handled; a variety
      of argillaceous slate.

   By a long chalk, by a long way; by many degrees. [Slang]
      --Lowell.

   Chalk drawing (Fine Arts), a drawing made with crayons. See
      Crayon.

   Chalk formation. See Cretaceous formation, under
      Cretaceous.

   Chalk line, a cord rubbed with chalk, used for making
      straight lines on boards or other material, as a guide in
      cutting or in arranging work.

   Chalk mixture, a preparation of chalk, cinnamon, and sugar
      in gum water, much used in diarrheal affection, esp. of
      infants.

   Chalk period. (Geol.) See Cretaceous period, under
      Cretaceous.

   Chalk pit, a pit in which chalk is dug.

   Drawing chalk. See Crayon, n., 1.

   French chalk, steatite or soapstone, a soft magnesian
      mineral.

   Red chalk, an indurated clayey ocher containing iron, and
      used by painters and artificers; reddle.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Chalk \Chalk\, v. t. [imp. & p. p. Chalked; p. pr. & vb. n.
   Chalking.]
   1. To rub or mark with chalk.
      [1913 Webster]

   2. To manure with chalk, as land. --Morimer.
      [1913 Webster]

   3. To make white, as with chalk; to make pale; to bleach.
      --Tennyson.
      [1913 Webster]

            Let a bleak paleness chalk the door.  --Herbert.
      [1913 Webster]

   To chalk out, to sketch with, or as with, chalk; to
      outline; to indicate; to plan. [Colloq.] "I shall pursue
      the plan I have chalked out." --Burke.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chalk
    n 1: a soft whitish calcite
    2: a pure flat white with little reflectance
    3: an amphetamine derivative (trade name Methedrine) used in the
       form of a crystalline hydrochloride; used as a stimulant to
       the nervous system and as an appetite suppressant [syn:
       methamphetamine, methamphetamine hydrochloride,
       Methedrine, meth, deoxyephedrine, chalk, chicken
       feed, crank, glass, ice, shabu, trash]
    4: a piece of calcite or a similar substance, usually in the
       shape of a crayon, that is used to write or draw on
       blackboards or other flat surfaces
    v 1: write, draw, or trace with chalk

Moby Thesaurus II by Grady Ward, 1.0:

217 Moby Thesaurus words for "chalk":
   air brush, alabaster, art paper, ballpoint pen, besnow, blackboard,
   blanch, blaze, blaze a trail, bleach, blemish, blotch, book, brand,
   brush, calcimine, calendar, camera lucida, camera obscura, canvas,
   cartoon, carve, catalog, chalk up, charcoal, check, check in,
   check off, chronicle, cicatrize, color, copy, crayon, crosshatch,
   cut, dapple, dash, dash off, daub, define, delimit, delineate,
   demarcate, depict, design, diagram, discolor, docket, doodle, dot,
   draft, draw, drawing paper, drawing pencil, drier, driven snow,
   easel, engrave, enroll, enscroll, enter, eraser, etiolate, file,
   fill out, fixative, fleck, fleece, flour, foam, freckle, frost,
   gash, grave, grizzle, ground, hatch, impanel, impress, imprint,
   incise, index, ink, inkhorn, inkstand, inkwell, inscribe, insert,
   invisible ink, ivory, jot down, lay figure, lead pencil, lily,
   limn, line, list, log, maggot, make a mark, make a memorandum,
   make a note, make an entry, make out, mark, mark down, mark off,
   mark out, matriculate, maulstick, medium, milk, minute, mottle,
   nib, nick, notch, note, note down, paint, paint a picture,
   paintbrush, palette, palette knife, paper, pastel, pearl, pen,
   pencil, pepper, picture, picturize, pigments, pipe-clay,
   place upon record, plume, point, poll, portray, post, post up,
   prick, print, punch, punctuate, puncture, put down, put in writing,
   put on paper, put on tape, quill, record, reduce to writing, reed,
   register, riddle, scar, scarify, score, scotch, scratch,
   scratchboard, scumble, seal, seam, set down, shade, sheet,
   siccative, silver, sketch, sketchbook, sketchpad, slate, snow,
   spatula, speck, speckle, splotch, spot, spray gun, stain, stamp,
   stencil, stigmatize, streak, striate, stripe, stump, style,
   stylograph, stylus, swan, sympathetic ink, table, tablet, tabulate,
   take down, tape, tape-record, tattoo, tick, tick off, tint, trace,
   underline, underscore, varnish, videotape, white, whiten,
   whitewash, write, write down, write in, write out, write up