The Collaborative International Dictionary of English v.0.48:

Extreme \Ex*treme"\, n.
   1. The utmost point or verge; that part which terminates a
      body; extremity.
      [1913 Webster]

   2. Utmost limit or degree that is supposable or tolerable;
      hence, furthest degree; any undue departure from the mean;
      -- often in the plural: things at an extreme distance from
      each other, the most widely different states, etc.; as,
      extremes of heat and cold, of virtue and vice; extremes
      meet.
      [1913 Webster]

            His parsimony went to the extreme of meanness.
                                                  --Bancroft.
      [1913 Webster]

   3. An extreme state or condition; hence, calamity, danger,
      distress, etc. "Resolute in most extremes." --Shak.
      [1913 Webster]

   4. (Logic) Either of the extreme terms of a syllogism, the
      middle term being interposed between them.
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   5. (Math.) The first or the last term of a proportion or
      series.
      [1913 Webster]

   In the extreme as much as possible. "The position of the
      Port was difficult in the extreme." --J. P. Peters.
      [1913 Webster]

The Jargon File (version 4.4.7, 29 Dec 2003):

in the extreme
 adj.

    A preferred superlative suffix for many hackish terms. See, for example,
    obscure in the extreme under obscure, and compare highly.