The Collaborative International Dictionary of English v.0.48:

Rutin \Ru"tin\ (r[udd]"t[i^]n), n. (Chem.)
   A glucoside resembling, but distinct from, quercitrin. Rutin
   is found in the leaves of the rue (Ruta graveolens) and
   other plants, and obtained as a bitter yellow crystalline
   substance which yields quercitin on decomposition.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rue \Rue\ (r[udd]), n. [F. rue, L. ruta, akin to Gr. "ryth`; cf.
   AS. r[=u]de.]
   1. (Bot.) A perennial suffrutescent plant (Ruta
      graveolens), having a strong, heavy odor and a bitter
      taste; herb of grace. It is used in medicine.
      [1913 Webster]

            Then purged with euphrasy and rue
            The visual nerve, for he had much to see. --Milton.
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            They [the exorcists] are to try the devil by holy
            water, incense, sulphur, rue, which from thence, as
            we suppose, came to be called herb of grace. --Jer.
                                                  Taylor.
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   2. Fig.: Bitterness; disappointment; grief; regret.
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   Goat's rue. See under Goat.

   Rue anemone, a pretty springtime flower (Thalictrum
      anemonides) common in the United States.

   Wall rue, a little fern (Asplenium Ruta-muraria) common
      on walls in Europe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Ruta graveolens
    n 1: European strong-scented perennial herb with grey-green
         bitter-tasting leaves; an irritant similar to poison ivy
         [syn: rue, herb of grace, Ruta graveolens]