If you rue the day that you did something, you are sorry that you did it, because it has had unpleasant results. You'll live to rue the day you said that to me, my girl. to wish that you had not done something = regret
If you rue something that you have done, you are sorry that you did it, because it has had unpleasant results. Tavare was probably ruing his decision. = regret
European strong-scented perennial herb with gray-green bitter-tasting leaves; an irritant similar to poison ivy