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.
      [1913 Webster]

            In a drought the thirsty creatures cry. --Dryden.
      [1913 Webster]

   2. Thirst; want of drink. --Johnson.
      [1913 Webster]

   3. Scarcity; lack.
      [1913 Webster]

            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]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "drought":
   absence, appetite, aridity, aridness, beggary, canine appetite,
   corkiness, defectiveness, deficiency, deficit, deprivation,
   destitution, dryness, emptiness, empty stomach, famine,
   hollow hunger, hunger, hungriness, imperfection, impoverishment,
   incompleteness, juicelessness, lack, need, omission, polydipsia,
   relish, saplessness, shortage, shortcoming, shortfall, starvation,
   stomach, sweet tooth, tapeworm, taste, thirst, thirstiness,
   torment of Tantalus, want, wantage, waterlessness,
   watertight integrity, watertightness



Easton's 1897 Bible Dictionary:

Drought
   From the middle of May to about the middle of August the land of
   Palestine is dry. It is then the "drought of summer" (Gen.
   31:40; Ps. 32:4), and the land suffers (Deut. 28:23: Ps. 102:4),
   vegetation being preserved only by the dews (Hag. 1:11). (See DEW.)