(r) v. rued, ru·ing v.t.
To feel sorrow or remorse for; regret extremely.
—v.i. To feel sorrow or remorse; be regretful. See synonyms under MOURN.
—noun
1. Sorrowful remembrance; regret.
2. Scot. Repentance. [OE hrēowan be sorry]
—ru′er noun

(r) noun
1. A small, bushy herb (Ruta graveolens) with bitter, acrid leaves, formerly much used in medicine for stimulating effects: formerly also an emblem of bitterness or grief.
2. An infusion made from this plant; hence, any bitter draft. [<F <L ruta <Gk. rhytē]