Source : Webster's Revised Unabridged Dictionary (1913)

Bittersweet \Bit"ter*sweet`\, a.
   Sweet and then bitter or bitter and then sweet; esp. sweet
   with a bitter after taste; hence (Fig.), pleasant but
   painful.

Bittersweet \Bit"ter*sweet`\, n.
   1. Anything which is bittersweet.

   2. A kind of apple so called. --Gower.

   3. (Bot.)
      (a) A climbing shrub, with oval coral-red berries
          ({Solanum dulcamara}); woody nightshade. The whole
          plant is poisonous, and has a taste at first sweetish
          and then bitter. The branches are the officinal
          dulcamara.
      (b) An American woody climber ({Celastrus scandens}),
          whose yellow capsules open late in autumn, and
          disclose the red aril which covers the seeds; -- also
          called {Roxbury waxwork}.

Source : WordNet®

bittersweet
     n 1: poisonous perennial Old World vine having violet flowers and
          oval coral-red berries; widespread weed in North America
          [syn: {bittersweet nightshade}, {climbing nightshade}, {deadly
          nightshade}, {poisonous nightshade}, {woody nightshade},
           {Solanum dulcamara}]
     2: twining shrub of North America having three-valved yellow
        capsules enclosing scarlet seeds [syn: {American
        bittersweet}, {climbing bittersweet}, {false bittersweet},
         {staff vine}, {waxwork}, {Celastrus scandens}]

bittersweet
     adj 1: tinged with sadness; "a movie with a bittersweet ending"
     2: having a taste that is a mixture of bitterness and sweetness
        [syn: {semisweet}]