The Collaborative International Dictionary of English v.0.48:

ague \a"gue\ ([=a]"g[-u]), n. [OE. agu, ague, OF. agu, F. aigu,
   sharp, OF. fem. ague, LL. (febris) acuta, a sharp, acute
   fever, fr. L. acutus sharp. See Acute.]
   1. An acute fever. [Obs.] "Brenning agues." --P. Plowman.
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   2. (Med.) A fever characterized by paroxysms of high fever
      and shaking chills.
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   3. The cold fit or rigor of malaria or any other intermittent
      fever; as, fever and ague.
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   4. A chill, or state of shaking, as with cold. --Dryden. AS
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   Ague cake, an enlargement of the spleen produced by ague.


   Ague drop, a solution of the arsenite of potassa used for
      ague.

   Ague fit, a fit of the ague. --Shak.

   Ague spell, a spell or charm against ague. --Gay.

   Ague tree, the sassafras, -- sometimes so called from the
      use of its root formerly, in cases of ague. [Obs.]
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