The Collaborative International Dictionary of English v.0.48:

Drought \Drought\ (drout), n. [OE. droght, drougth,
   dru[yogh][eth], AS. druga[eth], from drugian to dry. See
   Dry, and cf. Drouth, which shows the original final
   sound.]
   1. Dryness; want of rain or of water; especially, such
      dryness of the weather as affects the earth, and prevents
      the growth of plants; aridity.
      [1913 Webster]

            The drought of March hath pierced to the root.
                                                  --Chaucer.
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            In a drought the thirsty creatures cry. --Dryden.
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   2. Thirst; want of drink. --Johnson.
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   3. Scarcity; lack.
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            A drought of Christian writers caused a dearth of
            all history.                          --Fuller.
      [1913 Webster]

WordNet (r) 3.0 (2006):

drought
    n 1: a shortage of rainfall; "farmers most affected by the
         drought hope that there may yet be sufficient rain early in
         the growing season" [syn: drought, drouth]
    2: a prolonged shortage; "when England defeated Pakistan it
       ended a ten-year drought" [syn: drought, drouth]