Sour a. [Compar. Sourer superl. Sourest.]
 1. Having an acid or sharp, biting taste, like vinegar, and the juices of most unripe fruits; acid; tart.
    All sour things, as vinegar, provoke appetite.   --Bacon.
 2. Changed, as by keeping, so as to be acid, rancid, or musty, turned.
 3. Disagreeable; unpleasant; hence; cross; crabbed; peevish; morose; as, a man of a sour temper; a sour reply. “A sour countenance.”
 He was a scholar . . .
 Lofty and sour to them that loved him not,
 But to those men that sought him sweet as summer.   --Shak.
 4. Afflictive; painful. “Sour adversity.”
 5. Cold and unproductive; as, sour land; a sour marsh.
 Sour dock Bot., sorrel.
 Sour gourd Bot., the gourdlike fruit Adansonia Gregorii, and Adansonia digitata; also, either of the trees bearing this fruit. See Adansonia.
 Sour grapes. See under Grape.
 Sour gum Bot. See Turelo.
 Sour plum Bot., the edible acid fruit of an Australian tree (Owenia venosa); also, the tree itself, which furnished a hard reddish wood used by wheelwrights.
 Syn: -- Acid; sharp; tart; acetous; acetose; harsh; acrimonious; crabbed; currish; peevish.
 Tu·pe·lo n.  Bot. A North American tree (Nyssa multiflora) of the Dogwood family, having brilliant, glossy foliage and acid red berries.  The wood is crossgrained and very difficult to split. Called also black gum, sour gum, and pepperidge.
 Largo tupelo, or Tupelo gum Bot., an American tree (Nyssa uniflora) with softer wood than the tupelo.
 Sour tupelo Bot., the Ogeechee lime.
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 sour gum
      n : columnar tree of eastern North America having horizontal
          limbs and small leaves that emerge late in spring and
          have brilliant color in early fall [syn: black gum, pepperidge,
           Nyssa sylvatica]