To Rue

1. (obsolete, transitive) To cause to repent of sin or regret some past action.
2. (obsolete, transitive) To cause to feel sorrow or pity.
3. (transitive) To repent of or regret (some past action or event); to wish that a past action or event had not taken place.
4. (archaic, intransitive) To feel compassion or pity.
5. (archaic, intransitive) To feel sorrow or regret.

Usage notes

• Often used in the collocation “rue the day”.