1. [n]  leaves sometimes used for flavoring fruit or claret cup but should be used with great caution: can cause irritation like poison ivy
2. [n]  European strong-scented perennial herb with gray-green bitter-tasting leaves; an irritant similar to poison ivy
3. [v]  feel remorse for; feel sorry for; be contrite about

1. \Rue\, n. [F. rue, L. ruta, akin to Gr. ?; cf. AS. r?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.
            Then purged with euphrasy and rue The visual nerve,
            for he had much to see.               --Milton.
            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.
   2. Fig.: Bitterness; disappointment; grief; regret.
   {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.
   

2. \Rue\, v. t. [imp. & p. p. {Rued}; p. pr. & vb. n. {Ruing}.]
   [OE. rewen, reouwen, to grive, make sorry, AS. hre['o]wan;
   akin to OS. hrewan, D. rouwen, OHG. hriuwan, G. reun, Icel.
   hruggr grieved, hrug[eth] sorrow. [root] 18. Cf. {Ruth}.]
   1. To lament; to regret extremely; to grieve for or over.
      --Chaucer.
            I wept to see, and rued it from my heart. --Chapmen.
            Thy will Chose freely what it now so justly rues.
                                                  --Milton.
   2. To cause to grieve; to afflict. [Obs.] ``God wot, it rueth
      me.'' --Chaucer.
   3. To repent of, and withdraw from, as a bargain; to get
      released from. [Prov. Eng.]
   

3. \Rue\, v. i.
   1. To have compassion. [Obs.]
            God so wisly [i. e., truly] on my soul rue.
                                                  --Chaucer.
            Which stirred men's hearts to rue upon them.
                                                  --Ridley.
   2. To feel sorrow and regret; to repent.
            Work by counsel and thou shalt not rue. --Chaucer.
            Old year, we'll dearly rue for you.   --Tennyson.
   

4. \Rue\, n. [AS. hre['o]w. See {Rue}, v. t.]
   Sorrow; repetance. [Obs.] --Shak.
   

a garden herb (Ruta graveolens) which the Pharisees were careful to tithe (Luke 11:42), neglecting weightier matters. It is omitted in the parallel passage of Matt. 23:23. There are several species growing wild in Palestine. It is used for medicinal and culinary purposes. It has a powerful scent, and is a stimulant. (See MINT.)