Meaning of “regret” - Learner’s Dictionary

regret

verb [ T ] us uk /rɪˈɡret/ present participle regretting, past tense and past participle regretted
Do you regret what you said?I regret not buying that coat when I had the chance.Sue regrets not revising harder for the exam.I don't regret a thing.I don't regret making the decision.
BAD DECISION

B1 to feel sorry about a situation, especially something that you wish you had not done:

If you don't tell her the truth you'll regret it later.
[ + doing sth ] I really regret leaving school so young.
[ + (that) ] He began to regret that he hadn't paid more attention in class.
SORRY TO SAY formal

B2 used to say that you are sorry that you have to tell someone about a situation:

[ + to do sth ] We regret to inform you that the application has been refused.
[ + (that) ] The council regrets that the money is no longer available.

(Definition of “regret verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)