colchicum
  Various bulbous plants of the genus Colchicum, such as the autumn
  crocus.  The dried ripe seeds or corms (short thick solid food-storing
  underground stem) of the autumn crocus which yield colchicine.

collodion
  Highly flammable, colorless or yellowish syrupy solution of pyroxylin,
  ether, and alcohol, used as an adhesive to close small wounds and hold
  surgical dressings, in topical medications, and for making photographic
  plates.

colocynth (bitter apple)
  Old World vine (Citrullus colocynthis) bearing yellowish, green-mottled
  fruits the size of small lemons.  The pulp of the fruit is a strong
  laxative.

colombo (calumba)
  Root of an African plant (Jatrorrhiza palmata, family Menispermaceae)
  containing columbin; it is used as a tonic called calumba root or
  colombo root.

colostrum (foremilk)
  Thin yellowish fluid secreted by the mammary glands at birth, rich in
  antibodies and minerals.  It precedes the production of true milk.

coltsfoot (galax)
  Eurasian herb (Tussilago farfara), naturalized in parts of North America
  with dandelion-like flower heads.  Dried leaves or flower heads of this
  plant have been long used in herbal medicine to treat coughs.

consomme
  Clear soup or bouillion boiled down so as to be very rich.

contretemps
  Unforeseen disruption of the normal course of things; inopportune
  occurrence.

copaiba
  Transparent, often yellowish, viscous oleoresin from South American
  trees of the genus Copaifera in the pea family, used in varnishes and as
  a fixative in perfume.

copperas (ferrous sulfate)
  Greenish crystalline compound, FeSO4.7H2O, used as a pigment,
  fertilizer, and feed additive, in sewage and water treatment, and in the
  treatment of iron deficiency.

corrosive sublimate
  Mercuric chloride.

costal
  Relating to or near a rib.

costive
  Constipated

cranesbill (geranium, storksbill)
  Plants of the genus Geranium, with pink or purplish flowers.  Various
  plants of the genus Pelargonium, native chiefly to southern Africa and
  widely cultivated for their rounded and showy clusters of red, pink, or
  white flowers.

cream of tartar
  Potassium bitartrate.  White, acid, crystalline solid or powder,
  KHC4H4O6, used in baking powder, in the tinning of metals, and as a
  laxative.

Creasote (creosote)
  Colorless to yellowish oily liquid containing phenols and creosols,
  obtained by the destructive distillation of wood tar, especially from
  beech, and formerly used as an expectorant in treating chronic
  bronchitis.  Also used as a wood preservative and disinfectant.  May cause
  severe neurological disturbances if inhaled.

crepe de Chine
  Silk crepe used for dresses and blouses.