Learner's definition of AVENGE
to harm or punish someone who has harmed you or someone or something that you care about
The brothers vowed to avenge the death of their father.
They vowed to avenge their father by capturing and punishing his killer.
The team is out to avenge last week's defeat. [=to defeat the team that they were defeated by last week]
She vowed to avenge herself [=to get revenge], saying she would make him pay for what he had done to her.