The Collaborative International Dictionary of English v.0.48:

Altern \Al"tern\, a. [L. alternus, fr. alter another: cf. F.
   alterne.]
   Acting by turns; alternate. --Milton.
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   Altern base (Trig.), a second side made base, in
      distinction from a side previously regarded as base.
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The Collaborative International Dictionary of English v.0.48:

Base \Base\, n. [F. base, L. basis, fr. Gr. ba`sis a stepping,
   step, a base, pedestal, fr. bai`nein to go, step, akin to E.
   come. Cf. Basis, and see Come.]
   1. The bottom of anything, considered as its support, or that
      on which something rests for support; the foundation; as,
      the base of a statue. "The base of mighty mountains."
      --Prescott.
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   2. Fig.: The fundamental or essential part of a thing; the
      essential principle; a groundwork.
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   3. (Arch.)
      (a) The lower part of a wall, pier, or column, when
          treated as a separate feature, usually in projection,
          or especially ornamented.
      (b) The lower part of a complete architectural design, as
          of a monument; also, the lower part of any elaborate
          piece of furniture or decoration.
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   4. (Bot.) That extremity of a leaf, fruit, etc., at which it
      is attached to its support.
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   5. (Chem.) The positive, or non-acid component of a salt; a
      substance which, combined with an acid, neutralizes the
      latter and forms a salt; -- applied also to the hydroxides
      of the positive elements or radicals, and to certain
      organic bodies resembling them in their property of
      forming salts with acids.
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   6. (Pharmacy) The chief ingredient in a compound.
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   7. (Dyeing) A substance used as a mordant. --Ure.
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   8. (Fort.) The exterior side of the polygon, or that
      imaginary line which connects the salient angles of two
      adjacent bastions.
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   9. (Geom.) The line or surface constituting that part of a
      figure on which it is supposed to stand.
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   10. (Math.) The number from which a mathematical table is
       constructed; as, the base of a system of logarithms.
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   11. [See Base low.] A low, or deep, sound. (Mus.)
       (a) The lowest part; the deepest male voice.
       (b) One who sings, or the instrument which plays, base.
           [Now commonly written bass.]
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                 The trebles squeak for fear, the bases roar.
                                                  --Dryden.
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   12. (Mil.) A place or tract of country, protected by
       fortifications, or by natural advantages, from which the
       operations of an army proceed, forward movements are
       made, supplies are furnished, etc.
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   13. (Mil.) The smallest kind of cannon. [Obs.]
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   14. (Zool.) That part of an organ by which it is attached to
       another more central organ.
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   15. (Crystallog.) The basal plane of a crystal.
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   16. (Geol.) The ground mass of a rock, especially if not
       distinctly crystalline.
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   17. (Her.) The lower part of the field. See Escutcheon.
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   18. The housing of a horse. [Obs.]
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   19. pl. A kind of skirt (often of velvet or brocade, but
       sometimes of mailed armor) which hung from the middle to
       about the knees, or lower. [Obs.]
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   20. The lower part of a robe or petticoat. [Obs.]
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   21. An apron. [Obs.] "Bakers in their linen bases."
       --Marston.
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   22. The point or line from which a start is made; a starting
       place or a goal in various games.
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             To their appointed base they went.   --Dryden.
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   23. (Surv.) A line in a survey which, being accurately
       determined in length and position, serves as the origin
       from which to compute the distances and positions of any
       points or objects connected with it by a system of
       triangles. --Lyman.
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   24. A rustic play; -- called also prisoner's base, prison
       base, or bars. "To run the country base." --Shak.
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   25. (Baseball) Any one of the four bounds which mark the
       circuit of the infield.
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   Altern base. See under Altern.

   Attic base. (Arch.) See under Attic.

   Base course. (Arch.)
       (a) The first or lower course of a foundation wall, made
           of large stones or a mass of concrete; -- called also
           foundation course.
       (b) The architectural member forming the transition
           between the basement and the wall above.

   Base hit (Baseball), a hit, by which the batsman, without
      any error on the part of his opponents, is able to reach
      the first base without being put out.

   Base line.
       (a) A main line taken as a base, as in surveying or in
           military operations.
       (b) A line traced round a cannon at the rear of the vent.


   Base plate, the foundation plate of heavy machinery, as of
      the steam engine; the bed plate.

   Base ring (Ordnance), a projecting band of metal around the
      breech, connected with the body of the gun by a concave
      molding. --H. L. Scott.
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