Rue, v. t. [imp. & p. p. Rued; p. pr. & vb. n. Ruing.]
Etymology: [OE. rewen, reouwen, to grive, make sorry, AS. hreówan; akin to OS. hrewan, D. rouwen, OHG. hriuwan, G. reun, Icel. hruggr grieved, hrugedh sorrow. sq. 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 other Webster entries under this spelling
Rue, n.
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.
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.
Rue, n.
Sorrow; repetance. [Obs.] Shak.
Shades of meaning
Fernald has no entry of its own for rue; he lists it under mourn.
Where he writes about it:
One may grieve or mourn, regret, rue, or sorrow without a sound; he bemoans with suppressed and often inarticulate sounds of grief; he bewails with passionate utterance, whether of inarticulate cries or of spoken words. — from mourn
One is made to rue an act by some misfortune resulting, or by some penalty or vengeance inflicted because of it. — from mourn