The Collaborative International Dictionary of English v.0.48:

Counter \Coun"ter\, a.
   Contrary; opposite; contrasted; opposed; adverse;
   antagonistic; as, a counter current; a counter revolution; a
   counter poison; a counter agent; counter fugue. "Innumerable
   facts attesting the counter principle." --I. Taylor.
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   Counter approach (Fort.), a trench or work pushed forward
      from defensive works to meet the approaches of besiegers.
      See Approach.

   Counter bond (Law), in old practice, a bond to secure one
      who has given bond for another.

   Counter brace. See Counter brace, in Vocabulary.

   Counter deed (Law), a secret writing which destroys,
      invalidates, or alters, a public deed.

   Counter distinction, contradistinction. [Obs.]

   Counter drain, a drain at the foot of the embankment of a
      canal or watercourse, for carrying off the water that may
      soak through.

   Counter extension (Surg.), the fixation of the upper part
      of a limb, while extension is practiced on the lower part,
      as in cases of luxation or fracture.

   Counter fissure (Surg.) Same as Contrafissure.

   Counter indication. (Med.) Same as Contraindication.

   Counter irritant (Med.), an irritant to produce a blister,
      a pustular eruption, or other irritation in some part of
      the body, in order to relieve an existing irritation in
      some other part. "Counter irritants are of as great use in
      moral as in physical diseases." --Macaulay.

   Counter irritation (Med.), the act or the result of
      applying a counter irritant.

   Counter opening, an aperture or vent on the opposite side,
      or in a different place.

   Counter parole (Mil.), a word in addition to the password,
      given in time of alarm as a signal.

   Counter plea (Law), a replication to a plea. --Cowell.

   Counter pressure, force or pressure that acts in a contrary
      direction to some other opposing pressure.

   Counter project, a project, scheme, or proposal brought
      forward in opposition to another, as in the negotiation of
      a treaty. --Swift.

   Counter proof, in engraving, a print taken off from another
      just printed, which, by being passed through the press,
      gives a copy in reverse, and of course in the same
      position as that of plate from which the first was
      printed, the object being to enable the engraver to
      inspect the state of the plate.

   Counter revolution, a revolution opposed to a former one,
      and restoring a former state of things.

   Counter revolutionist, one engaged in, or befriending, a
      counter revolution.

   Counter round (Mil.), a body of officers whose duty it is
      to visit and inspect the rounds and sentinels.

   Counter sea (Naut.), a sea running in an opposite direction
      from the wind.

   Counter sense, opposite meaning.

   Counter signal, a signal to answer or correspond to
      another.

   Counter signature, the name of a secretary or other officer
      countersigned to a writing. --Tooke.

   Counter slope, an overhanging slope; as, a wall with a
      counter slope. --Mahan.

   Counter statement, a statement made in opposition to, or
      denial of, another statement.

   Counter surety, a counter bond, or a surety to secure one
      who has given security.

   Counter tally, a tally corresponding to another.

   Counter tide, contrary tide.
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The Collaborative International Dictionary of English v.0.48:

Extension \Ex*ten"sion\, n. [L. extensio: cf. F. extension. See
   Extend, v. t.]
   1. The act of extending or the state of being extended; a
      stretching out; enlargement in breadth or continuation of
      length; increase; augmentation; expansion.
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   2. (Physics) That property of a body by which it occupies a
      portion of space.
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   3. (Logic & Metaph.)
      (a) Capacity of a concept or general term to include a
          greater or smaller number of objects; -- correlative
          of intension.
      (b) the class or set of objects to which a term refers; --
          contrasted with intension, the logical specification
          which defines members of a class, being the set of
          attributes which are necessary and sufficient to
          recognize an object as a member of the class.
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                The law is that the intension of our knowledge
                is in the inverse ratio of its extension. --Sir
                                                  W. Hamilton.
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                The extension of [the term] plant is greater
                than that of geranium, because it includes more
                objects.                          --Abp.
                                                  Thomson.
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   4. (Surg.) The operation of stretching a broken bone so as to
      bring the fragments into the same straight line.
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   5. (Physiol.) The straightening of a limb, in distinction
      from flexion.
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   6. (Com.) A written engagement on the part of a creditor,
      allowing a debtor further time to pay a debt.
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   Counter extension. (Surg.) See under Counter.

   Extension table, a table so constructed as to be readily
      extended or contracted in length.
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