The Collaborative International Dictionary of English v.0.48:

Medium \Me"di*um\, n.; pl. L. Media, E. Mediums. [L.
   medium the middle, fr. medius middle. See Mid, and cf.
   Medius.]
   1. That which lies in the middle, or between other things;
      intervening body or quantity. Hence, specifically:
      (a) Middle place or degree; mean.
          [1913 Webster]

                The just medium . . . lies between pride and
                abjection.                        --L'Estrange.
          [1913 Webster]
      (b) (Math.) See Mean.
      (c) (Logic) The mean or middle term of a syllogism; that
          by which the extremes are brought into connection.
          [1913 Webster]

   2. A substance through which an effect is transmitted from
      one thing to another; as, air is the common medium of
      sound. Hence: The condition upon which any event or action
      occurs; necessary means of motion or action; that through
      or by which anything is accomplished, conveyed, or carried
      on; specifically, in animal magnetism, spiritualism, etc.,
      a person through whom the action of another being is said
      to be manifested and transmitted.
      [1913 Webster]

            Whether any other liquors, being made mediums, cause
            a diversity of sound from water, it may be tried.
                                                  --Bacon.
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            I must bring together
            All these extremes; and must remove all mediums.
                                                  --Denham.
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   3. An average. [R.]
      [1913 Webster]

            A medium of six years of war, and six years of
            peace.                                --Burke.
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   4. A trade name for printing and writing paper of certain
      sizes. See Paper.
      [1913 Webster]

   5. (Paint.) The liquid vehicle with which dry colors are
      ground and prepared for application.
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   6. (Microbiology) A source of nutrients in which a
      microorganism is placed to permit its growth, cause it to
      produce substances, or observe its activity under defined
      conditions; also called culture medium or growth
      medium. The medium is usually a solution of nutrients in
      water, or a similar solution solidified with gelatin or
      agar.
      [PJC]

   7. A means of transmission of news, advertising, or other
      messages from an information source to the public, also
      called a news medium, such as a newspaper or radio; used
      mostly in the plural form, i. e. news media or media.
      See 1st media[2].
      [PJC]

   Circulating medium, a current medium of exchange, whether
      coin, bank notes, or government notes.

   Ethereal medium (Physics), the ether.

   Medium of exchange, that which is used for effecting an
      exchange of commodities -- money or current
      representatives of money.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Culture \Cul"ture\ (k?l"t?r; 135), n. [F. culture, L. cultura,
   fr. colere to till, cultivate; of uncertain origin. Cf.
   Colony.]
   1. The act or practice of cultivating, or of preparing the
      earth for seed and raising crops by tillage; as, the
      culture of the soil.
      [1913 Webster]

   2. The act of, or any labor or means employed for, training,
      disciplining, or refining the moral and intellectual
      nature of man; as, the culture of the mind.
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            If vain our toil
            We ought to blame the culture, not the soil. --Pepe.
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   3. The state of being cultivated; result of cultivation;
      physical improvement; enlightenment and discipline
      acquired by mental and moral training; civilization;
      refinement in manners and taste.
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            What the Greeks expressed by their paidei`a, the
            Romans by their humanitas, we less happily try to
            express by the more artificial word culture. --J. C.
                                                  Shairp.
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            The list of all the items of the general life of a
            people represents that whole which we call its
            culture.                              --Tylor.
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   4. (Biol.)
      (a) The cultivation of bacteria or other organisms (such
          as fungi or eukaryotic cells from mulitcellular
          organisms) in artificial media or under artificial
          conditions.
      (b) The collection of organisms resulting from such a
          cultivation.

   Note: The growth of cells obtained from multicellular animals
         or plants in artificial media is called tissue
         culture.
         [Webster 1913 Suppl. +PJC]

   Note: The word is used adjectively with the above senses in
         many phrases, such as: culture medium, any one of the
         various mixtures of gelatin, meat extracts, etc., in
         which organisms cultivated; culture flask, culture
         oven, culture tube, gelatin culture, plate culture,
         etc.
         [Webster 1913 Suppl.]

   5. (Cartography) Those details of a map, collectively, which
      do not represent natural features of the area delineated,
      as names and the symbols for towns, roads, houses,
      bridges, meridians, and parallels.
      [Webster 1913 Suppl.]

   Culture fluid, Culture medium a fluid in which
      microscopic organisms are made to develop, either for
      purposes of study or as a means of modifying their
      virulence. If the fluid is gelled by, for example, the use
      of agar, it then is called, depending on the vessel in
      which the gelled medium is contained, a plate, a slant, or
      a stab.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

culture medium
    n 1: (bacteriology) a nutrient substance (solid or liquid) that
         is used to cultivate micro-organisms [syn: culture
         medium, medium]