What is the meaning of the word "abjure"?

Definitions:

Implies a strong and solemn rejection, usually in a public or official manner. VERB
- Faced with the pressure, the witness decided to abjure their previous testimony.
To formally reject or disavow a formerly held belief, usually under pressure. VERB
- In the medieval era, individuals accused of heresy were often required to abjure their beliefs or face severe punishment.
To formaly renounce, reject, or give up a belief, claim, or way of life, often under oath. VERB
- Under pressure from the authorities, he was forced to abjure his previous statements about the government.